White Sauce
Into a pan, add the butter and melt it over low heat, add and sauté the onion, add the garlic and sauté until all ingredients are lightly browned, add the wheat flour and cook until slightly thickened.
Gradually add the milk, stirring constantly.
Add the nutmeg, salt to taste, mix nonstop until slightly thickened.
Filling
In a skillet, fry the sausages, add the onion and fry them together.
Sliced Bread
Flatten each slice of crustless bread with a rolling pin, making them thinner.
To assemble, add a layer of white sauce to the bottom of a baking dish and spread evenly.
Add a layer of sliced bread, then the tomato sauce, and a layer of ham.
Add the second layer of white sauce, add all the sausages, a layer of mozzarella cheese, and a second layer of sliced bread.
Add some tomato sauce, another layer of ham, a layer of mozzarella cheese, more tomato sauce, the last layer of bread and the white sauce.
Top it with a layer of ham, mozzarella cheese and oregano to taste.
Bake in a preheated oven at 180°C (356°F) until the cheese has fully melted.