- 3 cups heavy cream
- 1 garlic clove, finely grated
- Pinch of freshly grated nutmeg
- Kosher salt and freshly ground pepper
- 2 1/2 pounds baking potatoes, peeled
- 1/2 cup freshly grated Parmigiano-Reggiano cheese
- 1/2 cup freshly grated pecorino cheese
- 1/4 cup chopped parsley
- 6 ounces baked ham, sliced 1/4 inch thick and cut into 1/4-inch cubes
- Preheat the oven to 400° and butter a shallow 9-by-13-inch baking dish. In a medium saucepan, bring the heavy cream to a simmer. Add the garlic and nutmeg and season with salt and pepper. Keep warm.
- Using a mandoline, slice the potatoes crosswise 1/8 inch thick. In a small bowl, combine the pecorino and Parmigiano cheese. Arrange one fourth of the potato slices in the prepared baking dish, overlapping them slightly. Sprinkle 1/4 cup of the cheese, 1 tablespoon of the parsley and one third of the ham over the potatoes. Repeat the layering two more times. Top with a final layer of potatoes and sprinkle with the remaining 1/4 cup of cheese. Pour the cream mixture over and around the potatoes.
- Bake for 25 to 30 minutes, until the potatoes are tender and bubbling and the top is golden brown. Let stand for 15 minutes. Sprinkle with the remaining 1 tablespoon of parsley and serve.
The unbaked gratin can be refrigerated overnight. Return to room temperature before baking.