Baked Lasagne

Make the ragu first, on another day if it suits you. It is three hours of work on its own, and a lasagne assembled around a rushed meat sauce tastes of the shortcut.

Heat the oven to 180C/350F.

Warm the milk with the bay leaf in a pan over medium heat for 4-5 minutes, until steam rises and the surface trembles, then take it off the heat.

Melt the 70g of butter in a heavy pan over medium-low heat.

Stir in the flour and cook for 2-3 minutes, stirring constantly, until the paste loosens, foams gently and smells of biscuit rather than raw flour.

Fish out the bay leaf and pour in a ladleful of the warm milk, whisking hard until the paste is smooth again before the next ladle goes in.

Carry on adding the milk a ladle at a time, whisking each one smooth. Tipping it all in at once leaves lumps that no amount of later whisking takes out.

Speed up to a steady stream once about half the milk is in and the sauce is already loose.

Simmer gently for 5-8 minutes, stirring, until the béchamel coats the back of a spoon and just falls off it.

Grate in nutmeg to taste from the quarter nutmeg and season with the 4g of fine salt.

Leave it looser than looks right, thin enough to pour rather than spoon. The dried sheets drink a surprising amount as they bake, and a thick béchamel gives you chalky pasta and a dry slab.

Check the packet on the sheets. Most modern ones go in dry; if yours ask to be boiled first, do it, because dry sheets that were meant to be boiled will still be hard in the middle after an hour.

Butter a 25x35cm baking dish at least 6cm deep with the 10g of butter.

Spread a thin smear of ragu across the base, just enough to stop the first sheets sticking.

Lay sheets over it in a single layer, edge to edge and barely touching. Overlapping them doubles the pasta in that spot and leaves a hard band running through the finished dish.

Snap sheets to fit the corners rather than leaving gaps.

Spread about a fifth of the ragu over the sheets in a thin, even layer.

Pour over a ladleful of béchamel and spread it to the edges with the back of the spoon.

Scatter over a small handful of the parmesan.

Build four more layers the same way, keeping every layer thin. A lasagne is built in five thin layers rather than three thick ones, and a dish loaded with sauce slides apart the moment a knife goes into it.

Finish with sheets, the last of the béchamel spread right to the corners, and the rest of the parmesan.

Set the dish on a baking tray to catch anything that boils over.

Bake for 40-45 minutes, until the top is blistered brown in patches and the sauce is bubbling slowly at the edges rather than sitting still.

Push a thin knife into the middle. It should meet no resistance at any depth; anything that grips is a sheet that has not softened, and that wants another 10 minutes covered with foil.

Rest the dish on the worktop for 30 minutes before cutting. This is not politeness — straight from the oven the layers have not set and every slice collapses into a puddle on the plate, where a rested one lifts out square.

Cut into 8 squares and lift them out with a fish slice.