Cut the eggplants into 1cm slices. Lay them in a single layer on a baking tray, and spray each side lightly with oil. Roast at 190°C (Gas Mark 5 / 375°F) for around 30 minutes, turning them over halfway. They should be fairly soft but not overly crispy.

Add a spoonful of tomato sauce to the bottom of a baking dish (mine was a 6 inch circle, but anything similar will be fine), and spread it around. Layer up the slices of roasted eggplant, the grated cheddar and the fresh mozzarella with the remaining tomato sauce. I made 3 layers of each in total, but it doesn't really matter. Top the dish with any remaining cheese, and the breadcrumbs.

Return to the oven for a further 30 minutes, until the topping is golden brown and crispy, and the sauce is bubbling around the edges.