Heat a knob of butter and a spoon of oil in a large frying pan. When foaming, add enough aubergine slices to cover the bottom of the pan. Fry until browned on both sides, then remove from the pan with a slotted spoon and drain on absorbent kitchen paper. Fry the remaining aubergine slices in this way, adding more oil and butter when necessary.

Fry the onion and garlic (if using) until golden in the same pan. Stir in the sieved tomatoes, tomato puree, oregano or basil, sugar, and salt and pepper to taste. Bring to the boil, then lower the heat and simmer for 5 minutes to reduce the sauce slightly.

Divide the aubergines into three equal portions and put one portion in the bottom of a shallow ovenproof dish.

Divide the tomato sauce into two and put one half on top of the aubergine layer. Spoon half of the yogurt on top of the tomato sauce. Repeat these three layers once more, then finish with the remaining portion of aubergines.

Sprinkle the top with the grated Parmesan and breadcrumbs. Bake in a moderate oven (180°C/350°F or Gas Mark 4) for 30 minutes or until the topping is golden brown and bubbling.