Classic Fish Pie with Peas & Lemon

Preheat oven to 180°C fan bake. Peel and chop the potatoes, then boil in salted water for 15–20 minutes until tender. Drain and mash with half the butter and a splash of the milk. Season well.

Place the white fish, salmon and prawns in a large saucepan, cover with the rest of the milk and bring to a gentle simmer. Poach for 4 minutes, then lift the fish out and flake into chunks, discarding any skin and bones. Reserve the poaching milk.

Peel and finely chop the onions and carrots. Heat the olive oil in a large saucepan over medium heat and cook them for 8 minutes until soft.

Add the remaining butter and stir in the flour for 1 minute. Gradually whisk in the reserved poaching milk to make a smooth sauce and simmer for 3–4 minutes until thickened. Stir in the mustard, the zest and a squeeze of juice from the lemon, the spinach and the peas, then fold in the flaked fish and prawns.

Pour the filling into a large baking dish. Spoon the mash over the top, rough up the surface with a fork and grate over the cheddar.

Bake for 30–35 minutes until golden and bubbling at the edges. Serve hot.