Peel and cut the eggplant lengthways into 1/4 inch thick slices. Leave them to sweat in a handful of coarse salt for about 2 hours. Rinse and wipe them dry in a cloth, then fry in a large quantity of oil and drain them on paper towels. Dip the eggplant slices into flour, shaking off the excess, then dip into the beaten eggs, seasoned with salt and pepper. Fry them again in the hot oil then drain. SautÄ the thinly sliced onion in the olive oil, pour the canned tomatoes and juice over, add a few basil leaves and cook for 30 minutes. Slice the mozarella. Spread a little of the tomato sauce in a gratin dish, cover with a layer of drained eggplants, then a few slices of mozarella and some freshly grated Parmesan. Build up the alternating layers to fill up the dish, ending with a layer of tomato sauce and cheese. Bake in a hot oven (500F) for 20 minutes.
