1. Heat your oven to 180C/Gas Mark 4.
2. Melt half the butter in a large omelette pan with a metal handle (so you can put it in the oven later). Season and fry the potato slices in batches until golden on each side, using more butter if required. Melt any remaining butter.
3. Whisk together the eggs, ricotta, cheddar, basil, baking powder, the remaining melted butter and some salt and pepper. Arrange the sliced potatoes in the pan and pour the mixture over, making sure everything is covered.
4. Transfer to the oven and bake for 25-30 minutes or until golden and risen.