1 Salt the aubergine slices and arrange on a plate. Peel the onion and dice very finely. Heat 1 tbsp oil in a pan, sweat the onions until translucent, then sprinkle with sugar and cook until lightly caramelised.
2 Add the tomatoes. Season the sauce with oregano, basil, salt and pepper and simmer over a low heat for about 15 minutes.
3 Meanwhile pat the aubergine slices dry with a piece of kitchen roll and brown lightly in oil, in batches.
4 Take out of the pan and drain on kitchen roll. Drain the mozzarella and slice thinly. Then lay a layer of aubergine slices in a greased baking dish, add a layer of tomato sauce and sprinkle with 1 tbsp Parmesan.
5 Continue in this way until all the aubergine slices are used up (use any remaining tomato sauce for another purpose).
6 Cover with the mozzarella slices and sprinkle with the remaining Parmesan. Bake in an oven preheated to 200°C (180° fan) | 400F | gas 6 for about 30 minutes until golden and bubbling.