Spray a 20 x 30 cm (8 x 12 inch) baking dish lightly with spray oil. Cut the aubergines into thin slices, brush the slices with the oil and season with a little salt and pepper. Cook under a preheated high grill for 2–3 minutes on each side until charred and softened.
Layer the aubergine slices, tomato sauce and mozzarella in the prepared baking dish to give 3 layers of each, ending with the mozzarella. Scatter over the Parmesan.
Bake in a preheated oven, 200°C (400°F), Gas Mark 6, for 20–25 minutes until bubbling and golden. Serve with a crisp green salad and some crusty bread.