Step 2

While that happens, pour the milk into a wide sauté pan, slide in the fish and bring it just up to the boil. Take it off the heat, cover, and leave it to stand for 3 minutes.

Step 3

Lift the fish out and keep the milk. Pat the fillets dry, then flake them in large pieces into an ovenproof dish, pulling away the skin and any bones as you go.

Step 4

Heat the second tablespoon of oil in a pan, stir in the flour and let it cook for 30 seconds. Add 7/8–1 cup of the poaching milk a splash at a time, stirring as you go, then grate in nutmeg, season, and let it bubble until it coats the back of a spoon. Stir in the cream.

Step 5

Heat the oven to 375°F/350°F fan/gas 5. Add the grated artichokes, sliced leek, shrimp, parsley and dill to the dish with the fish. Stir the lemon zest and juice into the sauce, pour it over, and turn everything through gently so the fish stays in pieces.

Step 6

Spread the mash over the top and drag a fork across it to raise ridges, which are what crisp in the oven. Scatter over the Gruyère and bake for 35–40 minutes, until golden and bubbling at the edges. Serve with wilted greens.