- 2 tbsp butter, at room temperature
- 3 leeks, white and light green parts only, split lengthwise, cut into thin slices and washed well
- 6 baking potatoes, peeled and cut into thin slices
- 3 tsp salt
- ¼ tsp freshly ground black pepper
- 2 cups heavy cream
- 1 cup gruyère cheese, grated
- Heat the oven to 300°F.
- Grease a two-quart gratin or shallow baking dish with butter.
- Spread half of the leeks in the dish and top with half of the potatoes.
- Sprinkle 1½ tsp of the salt and ⅛ tsp of the pepper.
- Layer the remaining leeks in the dish and top with the remaining potatoes.
- Sprinkle the remaining 1½ tsp salt and ⅛ tsp pepper.
- Pour cream over the potatoes and evenly sprinkle cheese on top.
- Bake the gratin until the potatoes and leeks are tender and the top is golden brown, for about 1½ hours.
- If the top has not browned sufficiently, broil for one or two minutes.