Add all of the ingredients for the meatballs to a very large bowl and knead them together using your hands. Once the ingredients have been well mixed, start making meatballs that are 1½ inches in diameter until all of the meat is used up.
Fry the meatballs in hot oil until they are brown all over.
Melt the butter in a pot and stir the flour in. Once the butter has frothed up, add the milk. Season with salt and pepper, stir everything well using a whisk, and take the pot from the heat once the sauce has been brought to the boil.
Fill the bottom of a casserole dish with half of the béchamel sauce, cover it with three lasagna sheets, and place 12 meatballs on top of them. Spoon a generous tablespoon of tomato sauce onto each meatball, sprinkle on a third of the mozzarella, and then add half of the cooked ham. Now proceed as follows: four lasagna sheets, béchamel sauce, cooked ham, mozzarella, four lasagna sheets, 12 meatballs, tomato sauce, mozzarella.
Bake the lasagna at 340°F in a convection oven for 40 minutes.
