The holidays call for delicious and rich sides. Adding mushrooms to potatoes au gratin makes for a decadent and varied take on the classic side dish. The potatoes form a crispy crust on a pie filled with wild mushrooms and two types of cheese.
This is a great dish to make if you have to bring a side to a holiday dinner. It can be assembled the day before the party and travels easily. It also pairs nicely with roast poultry and braised meats.
For the recipe,
2 tablespoons unsalted butter, plus more for dish
1 medium onion, cut into 1/2-inch dice
2 pounds assorted wild mushrooms, such as chanterelle, oyster, or black trumpet, coarsely chopped
1/4 cup dry white wine, such as Sauvignon Blanc
1 1/2 teaspoons coarse salt
Freshly ground pepper
1 cup finely grated Gruyere cheese (about 4 ounces)
1 cup finely grated Parmesan cheese, about 3 1/2 ounces
2 pounds Yukon gold potatoes, peeled and cut into 1/8-inch-thick rounds
1 tablespoon finely chopped thyme leaves
3/4 cup whole milk
1/2 cup heavy cream
- Preheat oven to 350 degrees. Butter a 13-by-9-inch baking dish; set aside.
- Melt butter in a large skillet over medium heat. Add onion; cook, stirring occasionally, until softened, about 5 minutes. Add half of the mushrooms; cook until they are slightly softened.
- Add remaining mushrooms; cook, stirring occasionally, until mushrooms have released their juices and most of the liquid has evaporated, 8 to 10 minutes.
- Add wine; cook, stirring occasionally, until liquid has evaporated, 3 to 5 minutes. Remove from heat. Season with salt and pepper.
- Combine cheeses in a small bowl; set aside.
- Cover bottom of prepared dish with potato slices, slightly overlapping them. Sprinkle with half of the thyme and a pinch each of salt and pepper. Sprinkle with 1/3 of the cheese and half of the mushroom mixture. Repeat layering process, using all but 2 tablespoons cheese.
- Arrange remaining potato slices, slightly overlapping, around the edge of the dish. Stir together milk and cream in a bowl, and pour over top. At this point, dish can be refrigerated, covered, up to 1 day; let stand at room temperature 30 minutes before baking.
- Cover loosely with foil, and bake until bubbling, about 1 hour. Remove foil, and sprinkle with reserved cheese. Bake until top is golden, 20 to 30 minutes more. Transfer dish to a wire rack; let cool 10 minutes before serving.
Serves 10 to 12.