Active Time

　　45 min

　　Total Time

　　2 hr

　　For a more elegant presentation, we cut out rounds from the gratin with a 4-inch cookie cutter.

　　Active time: 45 min Start to finish: 2 hr

　　

Ingredients

Makes 8 servings

　　1/2 lb fresh wild or exotic mushrooms such as chanterelles or shiitakes (discard shiitake stems), trimmed and coarsely chopped

　　2 1/2 tablespoons unsalted butter

　　3/4 lb fresh cremini mushrooms, trimmed and sliced 1/4 inch thick

　　1 1/2 teaspoons minced garlic

　　3 lb russet (baking) potatoes

　　1 1/2 cups heavy cream

　　1 1/2 cups whole milk

　　1 1/2 teaspoons salt

　　1/2 teaspoon white pepper

　　1/4 teaspoon freshly grated nutmeg

　　2 oz finely grated Gruyère (1 cup)

　　

Special Equipment

a 15- by 10- by 2-inch oval gratin dish or other 3-qt shallow baking dish

　　

Step 1

Put oven rack in middle position and preheat to 400°F.

　　

Step 2

Cook chanterelles or shiitakes with salt and pepper to taste in 1 tablespoon butter in a large nonstick skillet over moderate heat, stirring, until liquid mushrooms give off is evaporated and mushrooms are tender, about 8 minutes, then transfer to a bowl. Cook cremini in remaining 1 1/2 tablespoons butter in skillet, stirring, until liquid is evaporated and mushrooms are tender, about 8 minutes, then transfer to bowl with wild mushrooms. Toss mushrooms with 1 teaspoon garlic.

　　

Step 3

Peel potatoes and cut crosswise into 1/8-inch-thick slices (preferably with an adjustable-blade slicer). Bring potatoes, cream, milk, salt, white pepper, nutmeg, and remaining 1/2 teaspoon garlic to a boil in a 4- to 6-quart heavy pot, stirring once or twice, then remove from heat.

　　

Step 4

Transfer half of potatoes to buttered gratin dish with a slotted spoon, spreading evenly. Spread mushrooms evenly over potatoes, then top with remaining potatoes. Pour cooking liquid over potatoes and sprinkle with cheese.

　　

Step 5

Bake gratin until top is golden brown and potatoes are tender, 45 to 55 minutes. Let stand 10 minutes before serving.

　　Cooks' note:

　　•Instead of using 1/2 lb of 1 type of wild or exotic mushroom, you could use 1/4 lb each of 2 types.