Fish Pie with Cheesy Mash

Ingredients

• 300g cod fillets, cut into chunks
• 200g smoked haddock, cut into pieces
• 150g frozen peas
• 1 small onion, finely chopped
• 1 medium leek, trimmed and sliced
• 35g plain flour
• 900g potatoes, peeled and chopped
• sea salt and black pepper, to taste
• 500ml milk, divided
• 40g unsalted butter
• 120g cheddar, grated
• 1 tsp Dijon mustard (optional)
• 1 tbsp flat-leaf parsley, chopped
• Dressed green salad, to serve

Method

1. Preheat the oven to 200°C fan. Lay the cod and smoked haddock in a shallow pan with the bay leaf, pour over 200ml of the milk, cover and poach gently for 5–6 minutes until the fish is just flaky and opaque. Lift the fish out onto a plate and reserve the poaching milk; discard the bay.
2. Meanwhile, get the potatoes, celeriac and squash into a large pan of salted water and bring to the boil. Simmer for 15–18 minutes until everything is properly tender — a knife should slide through with no resistance.
3. While the mash cooks, melt the 40g butter in a wide pan over medium heat and sweat the onion and leek with a pinch of salt for 6–8 minutes until soft, sweet and translucent — don't let them colour. Stir in the flour and cook for a full minute to take the raw edge off the roux.
4. Slowly whisk in the reserved poaching milk and the remaining 300ml milk, a splash at a time, until you have a smooth, glossy sauce. Simmer for 3–4 minutes, stirring, until thick enough to coat the back of a spoon. Flake the fish into generous chunks and fold in with the peas, parsley and Dijon if using. Season carefully — the smoked haddock brings its own salt.
5. Drain the potatoes, celeriac and squash thoroughly and leave to steam-dry for a minute. Mash with the 25g butter and most of the cheddar until smooth and creamy, loosening with a splash of milk if needed. Taste and season.
6. Tip the fish filling into an ovenproof dish, then dollop the mash over the top in spoonfuls and spread to the edges with a fork, leaving rough peaks to catch in the oven. Scatter over the remaining cheddar.
7. Bake for 20–25 minutes until the top is deeply golden and the filling is bubbling visibly at the edges. Rest for 5 minutes so the pie firms up before serving.