Although simple, the flavours in this dish work perfectly together. The salty ricotta cheese, the sweet tomato sauce and the sweet and creamy aubergine. Note the trick of pre-soaking the aubergine to guarantee that it's sweet, without that bitter edge that you sometimes find with aubergines.
Parmesan cheese is not truly vegetarian, as it contains animal rennet. To make this dish 100% vegetarian, omit the cheese or find a suitable vegetarian substitute made without animal rennet. In supermarkets look for the 'parmesan style hard cheeses' which are suitable for vegetarians.