Courgettes cut very thin slices and fry in olive oil for 1 minute. Onions, tomatoes and mozzarella cut into thin slices. Grate the Parmesan. Spread plenty bottom and sides of pan with soft butter. Sprinkle with bread crumbs everywhere. Arrange a layer of zucchini, onion rings and tomatoes. Salt, ranking circles mozzarella and sprinkle with Parmesan. Arranged in this order until the products, the latter ends with zucchini and tomatoes. Add salt and sprinkle with a mixture of bread crumbs, Parmesan cheese and black pepper. Pour olive oil in a very thin stream and bake in preheated oven at 170 C 35-40 minutes until browned.