Preparation of the sauce, brown the onion in half of the butter and the oil. When golden, take it out and in its place, put the minced beef and the chicken livers in the saucepan, with the mashed tomato and chopped mushrooms.
Cook slowly for about an hour. Cut strips of pasta about 4” in width and boil in plenty of salted water, then drain when slightly underdone. Arrange layers of lasagna and sauce in a buttered baking dish sprinkle with Parmesan and put the pieces of remaining butter on top, then bake at medium temperature for approximately 15 minutes and serve.