Wild Mushroom Potato Gratin

I made this recipe for Thanksgiving dinner with my friends the Helms, and it was a hit. It was kinda of scary at first because I never made a potato gratin recipe before. I got this recipe from Debie Rose, a multi-line sales representative I work with. She is such a sweetheart and also a foodie addict. Debie collected more than 3000 recipe, and this is from one of her collections she found at epicurious.com.

For this recipe I used 3/4 lbs baby bella and 1/2 lbs shitake mushroom instead. Added mushroom buillon while the cream/milk was boiling and sprinkle some dried thyme over the guyere cheese. Also, use more cheese than it is called in the recipe.

yield: Makes 8 servings
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
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

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