Preheat the oven to 180°C. Arrange potato slices in a layer in a greased oven-proof dish. Cover with four tablespoons of cream and season with sea salt, black pepper and a sprinkle of ground nutmeg. Repeat until all the potato slices are nestled snugly in the rich nutmeg cream. Top with grated cheddar and Parmesan cheese. Bake for 40 minutes or until golden brown and bubbling. Serve hot with sea salt and freshly ground black pepper to taste.