Salmon & spinach fish pie with sweet potato

Preheat the oven to 200ªC, gas mark 6. Put the milk, stock and fish in a roasting tin. Cook for 12-15 minutes until the fish is just cooked through and no longer translucent – it should break into flakes. Using a fish slice, lift the fish onto a plate, reserving the liquid. Break the fish into large chunks, discarding any skin. Arrange, with the prawns, over the base of a shallow 2-litre ovenproof dish.

Wash the spinach and place in a pan with the water still clinging to the leaves. Wilt for 2–3 minutes, then drain thoroughly. Add to the fish in small spoonfuls.

Melt 50g of the butter in a medium pan, add the flour and cook for 1 minute. Off the heat, gradually add the reserved fishliquid, stirring each addition in and keeping the sauce smooth. Return to the heat and bring to the boil, stirring all the time, then simmer for 3-5 minutes stirring occasionally. Off the heat, stir in the dill and soured cream and season with the white pepper. Pour over the fish and leave to cool.

Cook the potatoes separately, in two large pans of boiling water for 15 minutes until tender. Drain and mash, then mix the remaining butter and seasoning into the plain potato. Stir the two mashes together but don’t over-mix. Spoon over the fish to completely cover. Cook for 35–40 minutes until golden brown and crisp on top. Serve with steamed broccoli or sugar snap peas.