As a son of the Dauphinois, the French region famous for its potato gratins, it would be unthinkable for me not to have at least one of these soul-soothing casseroles in my repertoire. Actually, I have several potato gratins in my files, but the potato-mushroom gratin - forestier always means there are mushrooms in the dish - is a favorite and one I've made for many years. Early in my career, I was the chef at the Baron of Beef, the famed
restaurant of the Hotel Plaza in Copenhagen. The restaurant was named for its specialty, a combination of two top rounds of beef carved tableside, and I always served the dish with a potato gratin, most often one like this in which the potatoes are layered with wild mushrooms, drenched with heavy cream and baked until they are soft, custardy and saturated with the cream. Topped with a dusting of Parmesan that browns as the potatoes bake, this gratin would sit easily next to
chicken or beef, or take center plate with a well-dressed salad on the side.
Makes 6 to 8 side-dish servings
- 1 pound assorted wild mushrooms, cleaned, trimmed and separated by variety
- 2 tablespoons (approximately) unsalted butter
- Salt and freshly ground white pepper
- 2 cloves garlic, peeled, split, germ removed, finely chopped
- ¼ teaspoon finely chopped thyme leaves
- 3 cups heavy cream
- Freshly grated nutmeg
- 4 pounds Idaho potatoes
- ¼ cup finely grated Parmesan cheese
1) Working in a medium sauté pan or skillet over medium heat, sauté each variety of mushroom in just enough butter to keep the mushrooms from sticking. Season the mushrooms with salt and pepper and cook, stirring, just until the mushrooms are tender but not colored, a few minutes for each batch. When one type of mushroom is cooked, drain, turn it into a bowl and repeat with the next type. You need to sauté the mushrooms separately because each type has a
different cooking time but, once cooked, all the mushrooms should be mixed together in the bowl, along with the garlic and thyme. Set aside at room temperature until needed. (The mushrooms can be sautéed up to 2 hours ahead and kept covered with plastic wrap at room temperature.)
2) Center a rack in the oven and preheat the oven to 350o F. Butter the bottom and sides of an ovenproof 10-inch sauté pan or skillet.
3) Pour the cream into a large bowl and whisk in salt, pepper and freshly grated nutmeg. (Add more salt than you might normally add because the potatoes will need it.) One at a time, peel the potatoes and slice them into 1/8-inch-thick rounds. The best way to get rounds this thin is to use a mandoline. Lacking that, use the thinnest slicing blade on the food processor or a knife. Toss the potatoes into the cream as you slice them.
4) Using your hands, pull enough potato slices out of the cream to make a single layer on the bottom of the pan, arranging the potatoes in even, slightly overlapping concentric circles. Make a second layer of potato slices and then pour some cream over the layers. Press down on the potatoes to compact the layers - when you do this, some of the cream should rise up between the slices. Spread the mushrooms (minus whatever liquid may have accumulated in the
bowl) over the potatoes and pour in more cream, again using your hands to press down on the ingredients and bring the cream to the top. Arrange the remaining potatoes in attractive layers over the mushrooms, pouring in cream and pressing down as you finish each layer. You may not need all of the cream - you'll know you've added enough cream when, without pressing down, you see cream at the edges. Dust the gratin evenly with the Parmesan cheese and place the gratin on a
foil-lined baking sheet that can act as a drip-catcher.
5) Bake the gratin 45 minutes, then check that it's not getting too brown. If necessary, lower the oven temperature to 300o F to keep the gratin from coloring too much. Bake 15 minutes more, or until you can easily pass a slender sharp knife through all the layers.
6) Remove the gratin from the oven and keep it warm about 20 minutes, time enough for the potatoes to soak up more cream. If it's more convenient, you can keep the gratin warm in a 200o F oven.
To serve: Bring the gratin to the table and cut it into wedges.
