Finely chop the onions, carrots, garlic and celery and sauté in a little olive oil with bay leaves. Add the meat and roast. Roast the tomato paste vigorously. Reduce the chopped tomatoes with the stock and a pinch of sugar. Deglaze with broth and reduce for 5 minutes. Add the wine and boil everything without the lid for about half an hour.
Cook the pasta in plenty of salted water according to the instructions on the package, drain and mix with the meat sauce.
Melt the butter, add the flour and sage and use it to make a roux. Pour in milk, season with salt, pepper and nutmeg. Stir with a whisk until the milk is liquid / creamy. Remove the sage.
First spread the bechamel in a saucepan. Fill the casserole halfway with pasta. Place sliced mozzarella on top, sprinkle half of the parmesan on top.
Fill the saucepan with the remaining pasta. Spread the bechamel on top. Scatter the rest of the parmesan on top.
Bake in the oven at 200 degrees for about 20-30 minutes. If necessary, use the grill to brown the top layer.