Make-Ahead: The mushroom mixture can be prepared 4 hours ahead, stored at room temperature.

A gratin is the French way to make scalloped potatoes. There are quite a few differences between the two. The main difference is that a gratin uses heavy cream. The high butterfat content in cream allows it to be baked for a long time without curdling, so a gratin can be prepared without the butter and flour that are needed to thicken the milk in scalloped potatoes. The result is rich and luxurious. Try this gratin with roast beef or tenderloin.

2 tablespoons unsalted butter
1 pound shiitake mushrooms, stemmed and cut into 1/2-inch slices
1/3 cup chopped shallots
5 large Idaho, russet, or eastern potatoes, peeled and thinly sliced (about 3 1/4 pounds)
2 cups heavy cream
1 cup chicken stock, preferably homemade, or use low-sodium canned broth
6 ounces Roquefort or blue cheese, crumbled
1/2 teaspoon salt
1/4 teaspoon freshly ground black pepper

1. Position a rack in the top third of the oven and preheat to 350°F. Lightly butter a 9- X 13-inch baking dish.

2. In a large skillet, heat the butter over medium heat. Add the mushrooms and cook, stirring often, until tender, about 10 minutes. Stir in the shallots and cook until softened, about 1 minute. Set aside.

3. In a medium saucepan, bring the cream and broth just to a simmer over medium heat. Remove from the heat and stir in the cheese until melted.

4. Spread half of the potatoes in the prepared dish and sprinkle with half of the salt and pepper. Top with the mushrooms, then the remaining potatoes. Season with the remaining salt and pepper. Pour the hot cream mixture over all. Cover tightly with foil.

5. Bake for 40 minutes. Remove the foil and continue baking until the potatoes are tender and the top is golden, about 40 more minutes. Let stand for 10 minutes before serving.