1) Preheat the oven to 190°C/gas mark 5.
2) Coat the bottom of a 23cm x 33cm baking dish with extra virgin olive oil. Arrange the courgette slices on the bottom of the dish and season with salt and freshly ground black pepper. Evenly pour over 80ml of the double cream and sprinkle with 1/3 of the mozzarella, 1/3 of the fontina and 2 tablespoons of the Romano. Sprinkle with 1/3 of the breadcrumbs. Repeat the layers, ending with the breadcrumbs.
3) Cut the butter into 1 1/3cm cubes and sprinkle over the top of the dish. Line a baking sheet with aluminium foil, place the baking dish on top and bake for 40 minutes until bubbling and the top is golden brown.