Start making the sauce by frying the chopped onion in a little olive oil, then add the tomato passata, some basil leaves and salt.
Simmer for half an hour.
Meanwhile, peel and thinly slice the aubergines, dip them in the batter to coat and then fry them in boiling olive oil, and finally transfer them to a paper towel to absorb the excess oil.
Make a thin layer of tomato sauce in the bottom of a non-stick oven dish and arrange the aubergine fritters on top without overlapping them.
Then make a layer of mozzarella slices, with a handful of parmesan cheese, a ladle of tomato sauce and proceed with the next layers.
Complete by covering the parmigiana with the tomato sauce, a sprinkling of parmesan cheese and a few knobs of butter.
Place in the oven at 200°C for about half an hour.
Serve hot or warm.
Great as an appetizer or main course.
Alternatively, make a diet version of parmigiana by replacing the fritters with simple grilled aubergines.