Classic lasagna

Method

1. Heat the olive oil in a large, heavy pan over a medium-low heat. Add the onion, carrot, celery and a pinch of salt and cook gently, stirring often, until soft, sweet and just starting to colour, 10 to 12 minutes. Stir in the garlic for the last minute.
2. Turn the heat up to high and add both minces. Break them up with a wooden spoon and keep cooking until the liquid has evaporated and the meat starts to sizzle and brown, 10 to 15 minutes. That browning is where the flavour comes from. Stir in the tomato paste and cook for 1 minute.
3. Pour in the wine and let it bubble until almost gone, about 2 minutes. Add the chopped tomatoes and the water, bring to the boil, then turn down to a gentle simmer. Part-cover and cook for 1 hour, stirring now and then, and adding a splash of water if it starts to catch on the bottom.
4. While the ragù simmers, start the béchamel. Warm the milk in a small pan until steaming. In a saucepan over a medium heat, melt the butter, whisk in the flour and cook for 1 to 2 minutes, stirring, until it smells biscuity but has not browned.
5. Add the warm milk a ladle at a time, whisking smooth before the next. Simmer gently for 5 minutes until it coats the back of a spoon, then season with nutmeg, salt and pepper. Press baking paper onto the surface so no skin forms while the ragù finishes.
6. When the hour is up, heat the oven to 190°C (170°C fan) and check the ragù. It should be rich and glossy but still loose, like a thick soup rather than a paste, because the dried pasta soaks up liquid as it bakes. If it holds its shape on a spoon, stir in up to 100ml more water. Season well with salt and pepper.
7. Whisk the béchamel, loosening it with a splash of milk if it has set too thick to spread. Use a 30 x 20cm dish and at least 6cm deep. Spread a thin layer of ragù over the base so the pasta cannot stick. Add 3 lasagna sheets, snapping them to fit, then a third of the remaining ragù, about a quarter of the béchamel and a small handful of parmesan.
8. Repeat twice more, so you have three layers of pasta, ragù, béchamel and parmesan. Finish with the last 3 sheets, then spread the rest of the béchamel over the top, right to the edges, since any bare pasta goes hard in the oven. Tear over the mozzarella and scatter with the remaining parmesan.
9. Bake on the middle shelf, with a tray on the shelf below to catch drips, for 40 to 45 minutes, until bubbling at the edges and deep golden in patches on top. If it colours too fast, lay a sheet of foil loosely over it. A knife pushed into the middle should meet no resistance from the pasta.
10. Leave it to rest for 15 minutes before cutting, so the layers set and slice cleanly instead of sliding apart. Serve with a crisp green salad. Cool any leftovers, cover and refrigerate within 2 hours, and reheat until piping hot all the way through.