I could go on about the rich, savoury filling of this Chicken Mushroom Pie—but let’s be honest, it’s the Duchess Potato topping that steals the show! 😅 Fluffy and buttery on the inside, with golden, crispy parmesan-crusted ridges on top… It’s the kind of thing you’ll want to peel off and devour one by one!

A chicken mushroom pie like no other!

This isn’t just any pie topping — it’s a show-stopping crown of creamy mashed potatoes, piped into golden swirls Duchess-style, brushed with butter, and sprinkled with parmesan before baking to crispy perfection. The ridges turn irresistibly crisp, the inside stays fluffy, and the base absorbs all the rich, savoury pie filling beneath. Move over, puff pastry — there’s a new king in town!

And what lies beneath that golden potato crown? A rich, hearty filling of tender chicken and meaty mushrooms bathed in a deeply savoury, dark sauce — the kind that tastes slow-cooked for hours, yet comes together in just 15 minutes.

This isn’t your average chicken pie. Originally dubbed the Extra Good Chicken Mushroom Pie (yes, I know — not my finest moment in naming!), it earns the title with a few simple but powerful upgrades: a splash of Guinness for bold depth (think Guinness Stew vibes), searing whole chicken pieces for better browning (more flavor!), and opting for beef stock over chicken for a richer, more robust sauce.

Small tweaks — big payoff.

PS You’ll feel like you’re decorating a cake when you pipe the mash. It’s oddly satisfying/amusing.

Ingredients for Duchess Potato Chicken Mushroom Pie

If you’re tempted to tally up the total butter in this recipe (I’m not doing the math for you!), just remember — we’re going for extra good here. 🥰 But if you must scale back (and only if it’s the doctor’s orders!), you can swap in oil spray to sear the chicken and lightly spritz the potato topping, and skip the second bit of butter in the mushrooms.

Just one rule: don’t skip the butter for the roux — or you might end up with a lumpy sauce. And nobody wants that. 🙂

1. CHICKEN FOR THE PIE

I prefer to use chicken thighs rather than breast for juicier bites of chicken. Though this is still very nicely made with breast (it won’t overcook), I just think it’s better with thigh.

2. PIE FILLING SAUCE AND OTHER STUFF

Here’s what you need for the other pie add-ins and the sauce:

Guinness beer – This is the secret ingredient that makes Irish Beef Stew one of the greatest in the world, giving the sauce a rich, dark brown colour and beautiful depth of flavour. It doesn’t taste beery at all because the alcohol is cooked out. Cans here in Australia are 470ml (16oz) so you’ll get two batches of this pie plus a few swigs for yourself out of a can (freeze leftover beer, it’s fine to use flat in cooking).See FAQ for gluten-free option, making this with wine instead of beer.
Beef stock – The other liquid for the sauce. Beef rather than chicken stock (the usual choice when cooking with chicken), for a darker brown sauce with deeper flavour.
Bacon – Thick-cut streaky works best, so you end up with nice pieces throughout the stew. The finely cut slices (which tend to be the more artisan style bacon) will work, but they are a bit too delicate for a stew situation – they curl and break.
Mushrooms – This is the main vegetable in this pie, so we’re using a good amount, 500g/1lb in total. I love the pops of juiciness they bring into the filling, and how they are a sponge for sauce. Substitute with carrots, celery and peas (pie favourites!)
Garlic and onion – Flavour base for the sauce. I like to cut the onion larger than usual – either 2.5cm/1″ squares or thick wedges – I just think it looks nicer in the sauce than having a gazillion tiny little diced pieces.
Thyme – Classic herb choice for this sauce, also used in Guinness Stew.
Flour – Thickens the sauce. Just regular plain/all-purpose flour. See FAQ for gluten-free option.
Tomato paste – Just 1 tablespoon thickens the sauce slightly and adds a touch of acidity to cut through the savouriness of the sauce. It was a late addition, and it’s definitely a more balanced sauce with it.
Butter – For cooking the mushrooms, chicken and making the roux (each cooked separately in this extra good pie recipe 🙂 ). You can cut down if using other vegetables that don’t absorb oil (like carrots) and use oil spray instead for browning the chicken. But you need the butter for the roux (ie the step when you mix flour in) as you need a minimum amount of fat else you’ll end up with a lumpy gravy.

3. DUCHESS POTATO TOPPING

And lastly, here’s what you need for the Duchess potatoes lid for this magnificent pie! Potatoes, butter and milk for the creamy mash, then parmesan (store-bought grated works best) and extra butter for drizzling for the topping.

Potatoes – Starchy potatoes, rather than waxy, are best, so the inside of the duchess potato swirls are fluffy inside with a light crust on the surface. Australia – Sebago are ideal (those dirt-brushed potatoes we get “everywhere”). US – Russet, and UK – King Edward or Maris Piper are perfect. Or any other starchy potatoes – Dutch creams, King Edwards or red delight.
Parmesan – News flash! Store-bought grated parmesan (the sandy type) works better here as it seems to nestle in the crevices better than finely grating your own. I find that grating my own is so light, like delicate snowflakes, you can end up with a layer that sits on top of the ridges of the swirls, which bakes up like a thin parmesan crisp rather than melting inside the ridges. (Am I really still writing about this? BUT THESE LITTLE DETAILS MATTER TO ME! #ThatCrazyHomeCook 😅)

How to make Duchess Potato Chicken Mushroom Pie

The order of cooking really matters here. Sear the chicken first, and you’ll end up with a burnt pan before you even start the sauce. Cook mushrooms with the onion and they just go watery without browning. And if you don’t reduce the Guinness before adding flour, the sauce tastes too beery because we’re not slow cooking for hours like we do Irish Guinness Stew.

So no, it’s not a quick throw-it-all-in-and-go recipe. But if you want a really good chicken pie, you’ve got one right here. 🙂

1. Filling

Use a large, deep, non-stick pan. Mine is 30cm/12″ wide – this one (shop around, I got mine for around $80, and no, that’s not an affiliate link!).

Garlic butter mushrooms first – Melt butter on high heat, add mushrooms and stir for 3 – 4 minutes until lightly coloured but still firm – they will finish cooking in the sauce. Add a bit more butter, melt, toss to coat, then add garlic, salt and pepper. Cook 20 seconds until garlic is golden, then transfer to a bowl, scraping out all the garlic bits (or they’ll burn).💡Adding the butter at the end is my trick for getting that rich buttery flavour on mushrooms without needing loads of butter at the start. Mushrooms are sponges for fat!
Golden seared chicken – Season with salt and pepper, then sear until nicely golden on both sides (~2 minutes). The chicken should still be raw inside – we finish cooking it through later. Once cool, cut into large 2.5cm/1″ pieces (I do this while the sauce is simmering).💡Searing whole gives better colour and flavour than chopped – both on the chicken and in the sauce (thanks to all those golden pan bits – fond!).

Bacon and onion – Lower the heat slightly so the golden bits stuck on the base of the pan don’t burn. Give the bacon a head start – cook for 20 seconds, then add the onion and cook until it’s starting to soften (~ 2 minutes). Add garlic and cook for another 20 seconds until golden.
Deglaze with Guinness – Add the beer, turn the heat up to high and simmer rapidly while you scrape the base of the pan to loosen any bits stuck on it. Simmer until reduced by about 75% – this will cook out the alcohol and beeriness, leaving behind a rich, savoury flavour that makes the sauce so special!

Roux – Add butter and let it melt, then sprinkle the flour across the surface and mix it in. It will look like thoroughly unappetising sludge – have faith! 🙂
Beef stock – While stirring the sludge in the pan, pour in half the beef stock, then keep mixing until the sludge dissolves – the liquid will become a very thick gravy.

Sauce thickness – Here’s how it looks at this stage. Very thick!
Simmer mushrooms – Then pour the remaining beef stock in, plus the water, tomato paste, salt and pepper. Stir to combine (it should be quite thin and watery), then add the mushrooms. Simmer for 10 minutes. During this time, the mushrooms will cook and the liquid will reduce and thicken into a gravy.

Add chicken – Once the sauce has thickened, add the chopped chicken and any accumulated chicken juices.
Thicken – Simmer for another 2 – 3 minutes until the gravy thickens slightly but remains saucy. However thick or saucy it is now, that’s how it will be inside the pie once baked. Goal thickness – when you drag a spoon across the base of the pan, the path should briefly hold before the liquid flows back over it (like pictured above).

PIPING THE DUCHESS POTATO TOPPING

Fill pan – Pour the filling into a 6 – 8 cup / 1.5 – 2 litre pan. You could put it in individual heatproof pie dishes or ramekins. Smooth the surface to create a flat bed for the Duchess Potatoes.Note: Unlike with Cottage Pie and Shepherd’s Pie, there’s no need to wait until the filling cools and firms up before topping with mash; you can proceed while the filling is still hot.
Pipe mashed potato topping – Fill a piping bag fitted with a star tip with hot, creamy mashed potato, then pipe mounds across the surface in any pattern you want. My swirls have a ~ 4cm/1.6″ base and are about 4cm / 1.4″ tall.No piping bag? No worries! Just snip off the corner of a ziplock bag and pipe smooth mounds. Else, spoon little lumps all over the surface (try to give them height!) or do a regular Cottage Pie topping (spread mash, rough up with a fork).

Little blobs – Use the remaining mash to pipe little swirls or blobs to fill gaps. I do this randomly – neatness isn’t the goal, I love the rustic, uneven look. Plus, everybody loves Duchess Potatoes, so squeeze in as many as you can!
Drizzle and sprinkle – Drizzle the butter all over, then sprinkle with parmesan.

BAKING

Bake for 30 minutes until the potatoes are tinged with gold and lightly crispy, and it’s bubbling around the edges. Note to self: If your pan is rather full (like mine), put a tray on the floor of the oven to catch drips!
Rest for 5 minutes, just to let it stabilise a bit before serving (if you serve it straight out of the oven, it’s a bit of a sloppy mess!). And if you’re feeling really fancy, sprinkle with a pinch of parsley for a dusting of green freshness.

HOW GOOD DOES THAT LOOK!!! And just wait until you taste it!

Use a large spatula or serving spoon so you can get a good amount of pie filling and potato topping together when serving. The Duchess Potatoes actually hold together quite well when scooped out.

Now. It’s time for you to come clean.

Be honest.

You want to pick off all the Duchess Potatoes and run away with them, too, right? 😈 Don’t leave me hanging!

Ingredients

Per/Cup

60 g / (4 tbsp) unsalted butter, approximately divided into 4 (no need to be accurate)
4 garlic cloves, finely minced
1 1/2 tsp cooking salt / kosher salt, divided (Note 1)
1 tsp black pepper, divided

Pie filling:

750 g / 1.5 lb chicken thighs, boneless skinless (Note 2)
500 g/1 lb button mushrooms – very small ones whole, larger ones halved or quartered
100 g / 3.5 oz thick-cut streaky bacon, cut into 2.5cm/1″ squares
1 1/2 onions , cut into 2cm/1″ square or thick wedges
2 sprigs fresh thyme (or 1/2 tsp dried thyme)
1/4 cup plain flour (all-purpose flour)
3/4 cup Guinness beer (Note 3)
1 1/2 cups beef stock/broth, low sodium
3/4 cup water
1 tbsp tomato paste

Mashed potato topping:

1 kg / 2 lb starchy potatoes, peeled, cut into 2.5cm / 1″ cubes (Note 4)
30g / 2 tbsp unsalted butter, cut into 1.5 cm / 1/2″ pieces
1/3 cup milk, hot
1/8 tsp white pepper (sub black)

Topping:

30g / 2 tbsp unsalted butter, melted (or olive oil spray)
2 tbsp grated parmesan, the sandy store-bought type works best or grate your own
2 tsp finely chopped parsley for garnish, optional

Now Cooking mode is on:

Instructions

ABBREVIATED RECIPE:

Brown mushrooms, remove, sear chicken (aggressively!) in the same pan, cut into large pieces. Sauté bacon, onion and garlic, deglaze with Guinness, make roux, add stock, simmer with mushrooms to thicken (~10 min). Add chicken towards the end. Pour into a baking dish, pipe on mashed potato, finish with butter and parmesan, bake 30 min.

FULL RECIPE:

Garlic butter mushrooms – Melt 1/4 of the butter in a large 30cm/12″ non-stick pan over high heat. Add mushrooms, toss for 3 – 4 minutes until you get some browning on the surface. Add another 1/4 of the butter, melt, and toss to coat. Add 1/4 tsp each salt and pepper and half the garlic, toss 30 seconds until garlic is golden – mushrooms will still be hard inside, they finish cooking later. Remove into a bowl (make sure you scrape out all garlic bits).
Sear chicken – Sprinkle the chicken with 1/2 tsp salt and 1/4 tsp pepper. In the same pan, melt another 1/4 of the butter until hot and foamy. Sear chicken 2 minutes on each side until nicely golden but inside is still raw (if they don’t fit in a single layer, do in batches). Remove onto plate, once cool enough to handle, cut into 2.5cm (1″) pieces.
Bacon and onion – In the same pan, add bacon and stir for 15 seconds, then add the onion (there should be enough fat from the chicken). Cook for 2 minutes until the onion edges are golden and starting to soften. Add remaining garlic and stir 20 seconds.
Deglaze with Guinness – Add Guinness and let it simmer rapidly, scraping the base of the pan to loosen any golden bits into the liquid (“fond” = free flavour!), until the Guinness is reduced down by 75%.
Sauce – Lower the heat to medium and add the remaining butter. Once melted, sprinkle flour all across the surface and stir for 1 minute – it will look pasty. While stirring, pour in half the stock. Keep stirring until the flour paste dissolves into the stock, for a lump-free sauce (yay!). Then add remaining stock, water, tomato paste, 1/4 tsp salt and 1/2 tsp pepper, stir well.
Simmer – Add the mushrooms plus all mushroom juices accumulated in the bowl into the pan. Simmer for 10 minutes or until the liquid reduces down into a fairly thick gravy and the mushrooms become soft. (Meanwhile, start the mash)
Thicken sauce – Add the chicken (plus all juices) and simmer for another 2 to 3 minutes until the gravy is quite thick and you can draw a path on the base of the pan. (Sauce thickness now = sauce thickness once baked). Taste – add more salt if needed (I don’t).
Assemble – Pour into a 1.5 – 2 L (6 – 8 cup) baking pan and smooth the surface. (Note 5 for other pan sizes)
Preheat oven to 200°C / 390°F (180°C fan-forced).
Duchess potato topping – Pipe mounds of mashed potato swirls on the surface. My swirls have a 4.5cm base (1.6″), about 4cm tall (1.4″), then I fill gaps with small swirls/blobs. I use all the mash! Drizzle with melted butter, sprinkle with parmesan. (Note 6 for no piping bag)
Bake for 30 minutes, rotating the pan at the 20-minute mark.
Serve – Rest for 10 minutes, sprinkle with parsley if using. Attack!

Mashed potato:

Make mash – Put the potatoes into a large pot of cold tap water. Bring to a boil over high heat, then cook for 15 minutes until soft. Drain, pass through a potato ricer (smoother) or mash well with a potato masher in the now-empty pot. Add butter, milk, 1/2 tsp salt and 1/8 tsp white pepper, stir through – it should be creamy but not loose (so it holds its form when piped).
Piping bag – Transfer mash into a piping bag fitted with a star tip. (Note 6 for no piping bag)

Recipe Notes:

1. Chicken breast will also work ok here, though thighs are juicier. Just cut into bite-sized pieces and sear the outside on high, sprinkling with salt and pepper. Remove from the pan and proceed with the recipe as written.

2. Salt – Halve for fine table salt, increase salt by 50% for flakes.

3. Guinness beer –Key for rich flavour in sauce despite short simmer time, so don’t skip it! Stout is also excellent. Non alcoholic Guinness – haven’t tried but I know 0% beer has improved drastically in recent years, so might be worth giving it a go!

Red wine (pinot, merlot, anything dry) – use 375ml / 1 1/2 cups. Sauce colour will be more like Beef Bourguignon, slightly more elegant (French!) flavour. I liked that version too but preferred Guinness (slightly richer and bolder).

4. Potatoes – Starchy potatoes work best here for fluffy insides and crispy outsides. Other starchy potatoes that work include: Dutch creams, King Edwards or red delight. Great all-rounders like Golden Delight, Coliban and Red Rascal are also great.

5. Pie dish – Use any you want. I was actually so tempted to make individual pies, but I can’t find my large ramekins. I dream of having copper single-serving-size gratin dishes. 🙂 Bake time will be the same.

6. No piping bag? No worries! Snip off the corner of a ziplock bag, or spoon dollops across the surface or just do it like Cottage Pie – spread mash across the surface, rough it up with a fork.

Leftovers will keep for 3 to 4 days in the fridge. If making ahead intentionally – fridge or freezer – make the sauce for the filling a little looser, top with mash, butter and parmesan, fully cool uncovered. Then cover and fridge/freezer (3 months). Fully thaw, then bake per recipe.

Nutrition per serving, assuming 6 servings.

Nutrition Information:

Calories:577cal (29%) Carbohydrates:43g (14%) Protein:36g (72%) Fat:29g (45%) Saturated Fat:14g (88%) Polyunsaturated Fat: 3gMonounsaturated Fat: 9g Trans Fat:1g Cholesterol: 176mg (59%) Sodium: 986mg (43%) Potassium:1535mg (44%) Fiber:4g (17%) Sugar:5g (6%) Vitamin A:633IU (13%) Vitamin C:15mg (18%) Calcium:88mg (9%) Iron:3mg (17%)

Duchess Potato Chicken Mushroom Pie

FAQ

Can this be made gluten-free?

The gluten in this recipe is from the Guinness (made with barley) and the flour used to thicken the sauce.

To make this gluten-free, use red wine instead of Guinness and make a cornflour slurry to thicken the sauce instead of flour. Use 2 1/2 tbsp cornflour (cornstarch) mixed with 1/4 cup water. Then, towards the end of the mushroom simmering time, pour that in slowly while stirring constantly. The sauce will thicken very quickly.

If still too thin for your taste, then make more cornflour slurry and add more.

How long will this keep for?

3 to 4 days in the fridge, or 3 months in the freezer. If making ahead, make the sauce a little thinner as it thickens overnight. You can also assemble them and bake later.

Note: cornflour-thickened sauce goes watery when reheated so if intentionally making ahead, use arrowroot instead (same amount and method). This is what we do at RTM.

Can I use the fancy poyayo topping on Cottage Pie and Shepherd’s Pie?

ABSOLUTELY!!! Use the 1.2kg/2.4lb potato called for in both the Cottage Pie and Shepherd’s Pie recipes and reduce the milk to just under 1/2 cup to make the mash a little stiffer so it’s pipable. Note – for those recipes, you’ll still need to wait for the filling to cool a bit (as per the recipe) so the mash doesn’t sink.

How did you come up with the idea for this recipe?

Truthfully, two things initiated today’s recipe. Firstly, I wanted to do a really cosy, comfort food dish because we’re in the height of winter right now here in Sydney.

Secondly, I’ve seen reports that mushroom sales have been down 15% because of the Erin Patterson case and even read articles that food media have consciously been avoiding mushroom recipes. I don’t think it’s cool that our mushroom farmers are suffering, so I want to do my part to change the tide. Mushrooms are good for you, they are delicious, so versatile, and one of my favourite vegetables. I will never stop!

So anyway, that’s what led me to do a big bubbly pie filled with lots of mushrooms. 🙂

Tell me about the development of this recipe?

Ugh, it was way harder than I expected. I was overly confident – it’s “my kind of food” and I’ve made loads of stews and pies before.

Firstly, I had it in my head that I wanted the pie to be a little special. It’s easy enough to make a quick’n ‘n easy chicken pie where you cook up everything in a pan in one go, throw in a little flour, stock and milk to make the sauce, then put a lid of puff pastry on it.

But chicken bites don’t brown like stewing beef, and it adds so much flavour to the meat when you get colour, not to mention the extra flavour you get in the sauce from the fond (brown bits) left in the pan from searing proteins.

So the first iterations I made using bite-sized chicken pieces were fine, but they just weren’t special. When I switched to searing whole chicken thighs to get a gorgeous golden sear on them and cutting them up later, that went some way to solving the flavour problem.

Then getting the right quantity of Guinness turned out to require a few more attempts than I expected. At first, I assumed more Guinness would equal more flavour, so I tipped the whole can in. It was so bitter, it bordered on inedible. 😅 The next attempt, I used 1 1/2 cups, and it was still too much. I was surprised, it’s not that much, but I underestimated how intense the flavour of stout beers is, especially when not slow cooking for hours like we do Guinness Stew.

Turns out, 3/4 cup is the limit for the quantity of sauce we need in this pie.

Throughout this, I also had to fiddle to get the sauce quantity and thickness right. This is something I grapple with every pie recipe. You’d think there’d be a standard formula – but there’s not. It depends on the shape of the meat (shredded meat works better with thinner sauce and holds more sauce too eg Chicken Pot Pie), the vegetables used (eg. broccoli are sauce hogs), chicken vs beef (chicken bites can’t be slow cooked so you need to get more flavour in less liquid faster as you don’t have sauce flavour development time like you get with slow cooked beef pie recipes like Meat Pies).

I also had a few fails with the piped topping. Firstly, getting the right consistency so it’s creamy but still pipeable and holds its form when baked (I had a couple of Duchess melting situations). And the piping tip matters too – if you use one that creates more ruffles (like Wilton 2D, which is a favourite for frosting), they look great when piped but don’t hold their form in the oven.

Turns out, a regular star tip works best!

I had a few more issues – major overflow in the oven, mushrooms not cooked through….. Let’s just say the builders have had a LOT of pie in recent weeks! 🙂

Chicken Mushroom Pie with Duchess Potato