Creamy Fish Pie with Cheesy Mash

Chunks of white fish and salmon in a smooth, herby white sauce under a fluffy cheddar mash topping. It's classic British comfort food that looks impressive but comes together with straightforward steps and everyday supermarket ingredients.

Fish pie feels like a treat but it’s mostly assembly. You poach the fish gently, build a glossy white sauce with a splash of the poaching milk, then blanket it all in buttery mash. Use a supermarket fish pie mix to save time, or pick your own combination of white fish, salmon and smoked haddock for real depth.

Ingredients

• 600 g fish pie mix — or a mix of cod, salmon and smoked haddock, skinless
• 400 ml whole milk
• 1 bay leaf
• 900 g floury potatoes — Maris Piper or King Edward, peeled and chunked
• 75 g butter — plus a little extra for the mash
• 50 g plain flour
• 100 g mature cheddar — grated
• 2 tbsp fresh parsley — chopped
• 1 tbsp Dijon mustard
• 2 large eggs — hard-boiled and quartered, optional
• 100 g frozen peas
• 1 lemon — zest and a squeeze of juice

Method

1. Heat the oven to 200C/180C fan/gas 6. Put the potatoes in a large pan of salted water, bring to the boil and simmer for 15-18 minutes until tender to the point of a knife.
2. Meanwhile, lay the fish in a wide pan and pour over the milk with the bay leaf. Bring to a gentle simmer and poach for 4-5 minutes, until the fish is opaque and flakes easily with no translucent flesh remaining. Lift the fish out with a slotted spoon and reserve the milk, discarding the bay leaf.
3. Melt the 75g butter in a saucepan, stir in the flour and cook for 1-2 minutes. Gradually whisk in the warm poaching milk, a little at a time, until you have a smooth, thick sauce. Simmer for 2-3 minutes, then stir in the mustard, parsley, lemon zest, half the cheddar and a good grind of pepper.
4. Drain the potatoes well and let them steam-dry for a minute, then mash with a knob of butter and a splash of milk until smooth. Season to taste.
5. Gently fold the poached fish, peas and a squeeze of lemon into the white sauce, keeping the fish in chunks. Tip into a 1.5 litre ovenproof dish and tuck the quartered eggs in, if using.
6. Spoon the mash over the top and spread to the edges to seal in the filling, roughing up the surface with a fork. Scatter over the remaining cheddar.
7. Bake for 30-35 minutes until the mash is golden and the sauce is bubbling up piping hot at the edges. Rest for 5 minutes before serving.

Serve it with

• Buttered greens or steamed tenderstem broccoli
• Minted garden peas
• A crisp green salad
• Crusty bread to mop the dish
• A wedge of lemon

Why this works

Poaching the fish in the milk you later use for the sauce means nothing is wasted and every bit of flavour ends up in the pie. A thick, well-cooked roux keeps the filling creamy rather than watery once baked.

Common swaps

• Swap cheddar for Gruyere or Parmesan for a nuttier topping
• Use half celeriac in the mash for a lighter, lower-carb top
• Stir in 100g raw prawns with the fish for a fuller seafood pie
• No fresh parsley? Use dill or chives instead
• Make it dairy-free with a plant butter and unsweetened oat milk

Common mistakes to avoid

• Over-poaching the fish so it dries out and breaks up; it finishes cooking in the oven
• A thin sauce that turns watery, add the milk slowly and simmer until properly thick
• Using waxy potatoes, which make gluey mash rather than a fluffy top
• Spreading the mash too thinly so the filling bubbles through instead of staying sealed

Storage, freezing & reheating

Storage: Cool leftovers quickly and keep covered in the fridge for up to 2 days.

Freezing: Freezes well assembled but unbaked, or once baked and cooled, for up to 3 months. Defrost fully in the fridge before baking or reheating.

Reheating: Reheat in a 180C/160C fan oven for 20-25 minutes until piping hot throughout. Cover with foil if the top browns too fast.

Allergen notes: contains Fish, Milk, Gluten, Egg, Mustard. Always check individual product labels.

Estimated nutrition

Per serving, estimated from typical ingredient values — not a substitute for precise dietary calculation.