PREPARATION
Wash the eggplant and cut into slices, arrange them in layers in a baking dish large and salt each layer. Repeat the same procedure with the marrows, arranging them in a separate container. Peel the potatoes, wash and cut into very thin slices, arranging them on a damp cloth.
Dip the tomatoes in boiling water to peel them easily, remove the skin and cut into four parts.
Fry the sliced eggplants ​​in 4 tablespoons of hot oil for 5 minutes, making sure that the slices do not overlap. Drain and set aside. Repeat the same operation with the potatoes and marrows, drying with a dry cloth.

Prepare the mixture of meat: place the meat in a bowl to which you add the onion and garlic finely chopped, cheese, breadcrumbs and a little 'salt and pepper, mix well together with a spoon.
Put cooking oil in a skillet set aside and add other two tablespoons, chop finely the rest of the onions and cook for 5 minutes over low heat, stirring constantly. Stir in the tomatoes, pepper and let cook a few moments everything.
Grease a large baking dish on the bottom and continue alternating layers of eggplant, meat mixture, slices of marrows, the mixture of meat, potatoes, and finally the layer of meat on the surface, each pair of alternating layers with chopped oregano, parsley and basil.

Prepare the sauce: In a saucepan, melt the margarine, add the flour and gradually the hot broth, stirring constantly.
Cook 5 minutes, then add the cheese, salt and pepper and pour the mixture on the pie, add a sprinkling of grated cheese and cover with a layer of bread crumbs and cover with butter.

Cover the pan with aluminum foil and place it on the middle shelf of the preheated oven. Cook 30 minutes at 200 ° C, then remove the aluminum and still continue cooking for 10 minutes at 240 ° C. After this time, turn off the oven but leave the flan still inside for another 10 minutes. Serve warm.