• Remove the skins from the salsiccia sausages and roughly chop the meat. Fry it in a splash of oil over a medium heat for about 5 minutes, until lightly golden.
• Add the onion and cook until soft and translucent, then add the garlic, carrot, courgette and celery. Fry for about 5 minutes, adding a little more oil if needed.

  Season with salt, freshly ground pepper and rosemary, and let the mixture simmer gently while you make the mornay sauce.

Béchamel/mornay

• Melt the butter in a saucepan, whisk in the flour and cook it through for a couple of minutes, whisking all the while.
• Add the milk in a couple of additions, whisking well each time, and finally stir the Parmesan into the sauce until it melts. Let the sauce simmer for 5-6 minutes, whisking now and then, and season to taste with salt and freshly ground pepper.

Assembling the lasagne

• Grease the dish with a little oil, and trim the lasagne sheets with scissors or a knife so they fit the dish.
• Spread a thin layer of filling over the base of the dish, top with a little mornay sauce and a layer of lasagne sheets. Use only a little at a time, and aim for 5 layers of pasta so the lasagne gets a good height.

  Continue with the next layers in the same way until almost all the filling and sauce have been used – save a little for the top.
• Spread the last of the filling over the top, and tear the mozzarella into pieces over it.
• Bake the lasagne in a preheated conventional oven (top and bottom heat) at 180°C for about 35 minutes, and let it rest for 15 minutes before serving.