Preheat the oven to 200 °C/gas 6.

Slice the aubergines into 1/2" strips. Salt both sides, wrap in kitchen paper and weigh down for 30 minutes. Brush off the salt, rinse and pat dry. Drizzle some oil on a grill pan and grill the aubergine slices until they are browned.

Chop the onions and fry them in olive oil until browned. Heat the tinned tomatoes gently in a saucepan with the sugar, and add the garlic after a few minutes. Add the pepper and salt, then some shredded basil and the browned onions.

Slice the mozzarella. Brush olive oil on the base and sides of a large casserole dish. Layer the aubergine and mozzarella slices, adding the tomato sauce and a sprinkling of parmesan to taste. Bake for 45 minutes.