Anna Louise I have made fish pie in many forms over the years — the classic version on this site, the leek version, the rosti-topped version — and this cheesy mash version is the one I make when I want maximum comfort and maximum impact. The cheesy mash topping is the defining feature.
Mashed potato enriched with mature Cheddar and a little Parmesan, spread over the cream filling and baked until the top is deeply golden and the cheese has formed a slightly crispy, slightly caramelised crust — it is the most satisfying thing to scoop through with a large spoon before serving.
The filling beneath is the reliable fish pie cream sauce I make every time — white fish, smoked haddock, and prawns in a cream and mustard sauce with dill and lemon. The cheesy mash takes it from wonderful to genuinely spectacular.
This is the fish pie I make for people who say they find fish pie slightly worthy and slightly dull. It is the version that changes their minds.
Ingredients for Mary Berry Fish Pie with Cheesy Mash
For the Fish Filling
- 300g skinless cod or haddock fillet, in large chunks
- 200g skinless smoked haddock fillet, in large chunks
- 150g large raw king prawns, peeled
- 600ml whole milk
- 1 bay leaf, 6 black peppercorns, slice of lemon — for poaching
For the Cream Sauce
- 50g unsalted butter
- 50g plain flour
- The strained poaching milk (approximately 550ml), warmed
- 150ml double cream
- 1 tsp Dijon mustard
- 2 tbsp fresh dill, chopped
- 2 tbsp fresh flat-leaf parsley, chopped
- Juice of ½ lemon
- Salt and freshly ground white pepper
For the Cheesy Mash Topping
- 1.2kg floury potatoes (Maris Piper), peeled and roughly chopped
- 75g unsalted butter
- 100ml warm whole milk or double cream
- 100g mature Cheddar, coarsely grated — half into the mash, half over the top
- 25g Parmesan, finely grated — half into the mash, half over the top
- Salt and white pepper
How to Make Mary Berry Fish Pie with Cheesy Mash
Step 1 — Poach the Fish
Place the white fish and smoked haddock in a wide, shallow pan. Pour over the milk. Add the bay leaf, peppercorns, and lemon slice. Bring to a very gentle simmer and poach for five to six minutes until just beginning to flake. Lift out carefully with a slotted spoon. Strain and reserve the poaching milk — it is now deeply flavoured with the fish and forms the base of the cream sauce. The prawns do not need poaching.
Step 2 — Make the Cheesy Mash
Boil the potatoes in well-salted water until completely tender. Drain thoroughly. Return to the pan and dry over a low heat for two minutes — this removes excess moisture and gives a better mash. Pass through a ricer or mash until smooth. Beat in the butter and warm milk or cream until silky. Add half the Cheddar and half the Parmesan. Stir through until the cheese has melted into the mash. Season very generously.
The mash should be slightly stiffer than eating consistency — it needs to hold its shape on top of the filling rather than sinking into it.
Step 3 — Make the Cream Sauce
Melt the butter in a large saucepan over a medium heat. Add the flour — stir for one to two minutes. Add the warm poaching milk gradually, whisking continuously until smooth. Bring to the boil and cook, stirring, until the sauce is thick and coats the back of a spoon generously. Add the cream and mustard. Stir through. Add the dill, parsley, and lemon juice. Season carefully — the smoked haddock makes the poaching milk quite salty, so taste before adding any salt.
Step 4 — Combine and Cool
Preheat your oven to 200°C / 180°C fan / Gas 6.
Gently fold the poached white fish, smoked haddock, and raw prawns into the cream sauce. Transfer to a large, deep ovenproof dish approximately 30x20cm. Leave to cool for ten minutes — this prevents the hot filling from melting the mash topping during assembly.
Step 5 — Top, Cheese and Bake
Spoon the cheesy mash over the filling in generous spoonfuls, then spread evenly to cover completely. Rough up the surface with a fork — the ridges and peaks crisp and brown beautifully. Scatter the remaining Cheddar and Parmesan over the entire surface.
Bake for 25 to 30 minutes until the cheesy mash topping is deeply golden, the cheese is slightly caramelised and crispy at the peaks, and the filling is bubbling at the edges.
Rest for five minutes before serving.
My Top Tips For Best Fish Pie with Cheesy Mash
Dry the potatoes before mashing. Returning the drained potatoes to the pan and cooking over a low heat for two minutes drives off the surface moisture that makes mash watery. Dry potatoes give a mash that is denser and richer — which is exactly what is needed for a topping that holds itself on top of a liquid filling.
The mash must be slightly stiffer than eating consistency. If the mash is too soft and loose it sinks into the filling during baking and the finished pie has no distinct layers when served. Stiff mash holds above the filling and gives that definitive scoop of cheesy mash with every portion.
Use both Cheddar and Parmesan in the mash and on top. The Cheddar gives a sharp, familiar, deeply cheesy flavour and melts into the mash beautifully. The Parmesan gives a slightly nutty, more intense seasoning and crisps more dramatically on the surface. Together they give a mash that is more complex and more interesting than either alone.
Cool the filling for ten minutes before topping. Hot filling immediately beneath fresh mash means the mash begins to slide and sink before the pie even goes into the oven. Ten minutes of cooling gives the sauce time to thicken slightly and hold the mash in place during baking.
Rough up the mash surface with a fork. Every peak and ridge browns and crisps during baking, giving a varied surface of golden, slightly caramelised cheese — far more interesting than a smooth, uniform top.
Serving Suggestions
With steamed peas alongside — their freshness is the perfect contrast to the rich, cheesy pie. With a simple green salad. On its own — a generous portion of this pie needs nothing alongside at all.
How to Store Fish Pie with Cheesy Mash
In the fridge: Store covered for up to 2 days. Reheat covered with foil at 180°C for 25 minutes — remove the foil for the final five minutes to re-crisp the cheesy mash topping.
In the freezer: Freeze assembled before baking for up to 2 months. Cover tightly. Defrost overnight and bake as directed, adding ten minutes.
Mary Berry Fish Pie with Cheesy Mash Recipe
Ingredients
Method
- Poach white fish and smoked haddock in milk with bay leaf, peppercorns, and lemon — 5–6 minutes. Lift out. Strain and reserve milk.
- Boil potatoes — drain, dry in pan 2 minutes. Rice or mash until smooth. Beat in butter and milk. Add half the Cheddar and half the Parmesan — stir until melted. Season very generously. Set aside.
- Melt butter, add flour — stir 1–2 minutes. Add warm poaching milk gradually — whisk smooth. Thicken over heat. Add cream and mustard. Add dill, parsley, and lemon juice. Season carefully — taste before adding salt.
- Preheat oven to 200°C / 180°C fan / Gas 6. Fold poached fish and raw prawns into cream sauce gently. Transfer to dish. Cool 10 minutes.
- Spoon cheesy mash over filling — spread evenly. Rough up surface with a fork. Scatter remaining Cheddar and Parmesan over the top.
- Bake 25–30 minutes until deeply golden, cheese caramelised at the peaks, and filling bubbling at the edges. Rest 5 minutes. Serve.
Notes
Frequently Asked Questions
Can I add salmon to the filling?
Yes — 150g of fresh salmon fillet, poached with the other fish and flaked into the filling, gives a richer, more varied result. Salmon and smoked haddock together are a particularly good combination.
Can I use sweet potato for part of the mash?
Yes — half Maris Piper and half sweet potato gives a golden, slightly sweeter mash that suits the cheesy topping beautifully. The sweet potato also gives the top a more vivid golden colour.
Can I add leeks to the filling?
Yes — two large leeks, finely sliced and cooked gently in butter for twelve minutes until completely soft, added to the cream sauce before the fish, give a sweet, silky addition that is very good. See the fish pie with leeks recipe on this site.
Why is my cheesy mash sinking into the filling?
The mash was too soft, the filling was too hot when the mash was added, or both. Make the mash stiffer by returning it to the pan and drying it briefly. Cool the filling fully before topping.
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