Potato Gratin with Porcini Mushrooms

Creamy and earthy the perfect accompaniment to a roast turkey, chicken or pork.

10 Servings
1/2-1 ounce dried porcini mushrooms
1 cup hot water
1/2 cup dry white wine
3 garlic cloves, halved
4 thyme sprigs
2 1/2 cups heavy cream
1 1/2 cups freshly grated Parmigiano-Reggiano cheese (5 ounces)
1 tablespoon kosher salt
1/8 teaspoon cayenne pepper
2 pounds Yukon Gold potatoes, peeled and sliced 1/8 inch thick on a mandoline

1. Preheat the oven to 350°. In a small bowl, cover the porcini with the hot water and let soak until rehydrated, about 20 minutes. Carefully remove the porcini from the soaking liquid and coarsely chop the porcini. Reserve the cooking liquid, strain to remove any dirt.
2. In a large saucepan, combine the reserved soaking liquid, wine, garlic and thyme sprigs and boil over high heat until the wine has reduced by half. Add the cream, 1 cup of the grated cheese, the salt and cayenne and bring to boil. Remove from the heat and discard the thyme sprigs and garlic cloves.
3. Arrange half of the potato slices in an even layer in a shallow, 9 inch baking dish. Spread the porcini evenly over the potatoes. Top with the remaining potato slices. Pour the cream mixture on top and tap dish gently on the counter and shake to distribute the cream. Sprinkle with the remaining 1/2 cup of grated cheese. Bake for 1 hour and 10 minutes, or until the potatoes are tender and the top is richly browned. Let the gratin rest for 15 minutes, before serving.

Adapted from Richard Betts.