Step 2

Start the potatoes in cold salted water and simmer until a knife meets no resistance, about 20 minutes. Drain them properly — wet potatoes make a slack topping.

Step 3

While the potatoes simmer, melt the butter in a saucepan and turn the leeks through the fat. Cover and sweat them gently for ten minutes, until collapsed and sweet, then take the pan off the heat.

Step 4

Mash the drained potatoes with the butter and milk until smooth, then season with pepper. Set the mash aside to firm up while you make the sauce.

Step 5

Whisk the flour into the wine in a small bowl until no lumps remain. Chase every lump now — this is what thickens the sauce.

Step 6

Pour the milk over the leeks, bring to the boil, then whisk in the wine paste. Keep stirring until it thickens enough to coat the back of a spoon.

Step 7

Season, then fold in the parsley, salmon, haddock and smoked haddock. Two minutes over the heat is plenty; the fish finishes in the oven.

Step 8

Spoon the filling into an ovenproof dish and tuck the halved eggs in among it. Let it cool until set, about 20 minutes, before the mash goes on, or the topping sinks straight through.

Step 9

Spread the mash over the top and rough the surface up with a fork. Scatter the Gruyère over — those ridges are what catch and brown.

Step 10

Bake for thirty to forty minutes, until the top is golden, the edges bubble and the fish is cooked through. Give it a few minutes out of the oven before you cut it.