Seafood

Preheat the oven to 400°F.
Place potatoes in a saucepan of cold salted water, bring to the boil and simmer until tender.
Drain and mash the potatoes with the butter and milk; season to taste.
Melt the butter in a saucepan, add the sliced leeks, cover and simmer until soft (about 10 minutes).
Whisk the plain flour and white wine together until smooth.
Add the milk to the leeks, bring to the boil, then add the flour–wine mixture and stir briskly until thickened.
Add the parsley and the fish, stir over the heat for 2 minutes, then spoon the filling into an ovenproof casserole.
Scatter the eggs over the filling and allow to cool until firm.
Spoon the mashed potatoes over the fish filling, mark with a fork and sprinkle with Gruyere.
Bake until lightly golden on top and bubbling around the edges, 30–40 minutes.