Drizzle the bottom of a baking dish with olive oil and cover it with a layer of eggplants, slightly overlapping them. Spread some tomato sauce over them, some basil leaves, mozzarella cheese, and finish with Parmesan cheese. Then another layer of eggplant and repeat the whole process to complete 3 or 4 layers. Cover the top layer with tomato sauce, mozzarella and lots of Parmesan cheese.