2. In a saucepan, melt the butter over medium heat. Add the leeks and cook until soft, about 5 minutes.
3. Layer half of the sliced potatoes in a greased baking dish. Season with salt and pepper.
4. Spread the cooked leeks over the potatoes. Add another layer of the remaining potatoes on top.
5. Pour the heavy cream over the potatoes and leeks. Sprinkle the grated cheese evenly on top.
6. Cover the baking dish with aluminum foil and bake for 40 minutes. Remove the foil and bake for an additional 20 minutes, or until the top is golden and bubbly.
7. Let the casserole cool for a few minutes before serving.
Notes:
Feel free to add some cooked bacon or ham for extra flavor.