Potato-Mushroom Gratin

I have always been a sucker for creamy potato dishes, so when I read about the Potato-Mushroom Gratin in the December 2008 issue of Bon Appetit I knew I needed to try the recipe out. Variations of potato gratins are always popular at my house, and adding mushrooms was a great enhancement I wouldn't have thought of on my own. This was a pretty simple dish, and I just walked around the grocery store with the magazine guiding me when I decided to make this last night.

I tweaked it enough that it became my own creation, but the following Bon Appetit recipe was my guide. I added thinly sliced shallots to each layer, which added a nice flavor. I did 1/2 Parmesan cheese and 1/2 emmentaler cheese, but only because that's what was in the fridge. The combination was nice, but I might stick with just Parmesan if I managed to plan better next time! The only other change I did was to use 2% milk instead of heavy cream, because I had some 2% milk left over from baking that I wasn't planning to drink. I wouldn't recommend this substitution, because it turned out runnier than I would have liked. Next time I make this I think I'll use fat free half and half, because it will have a better texture while still being lighter than heavy cream. I felt like my first stab at this dish was not perfect, but the flavors were enough to make up for the slightly watery texture. I have a feeling this dish will be just about perfect with a few adjustments next time.

Potato-Mushroom Gratin, from Bon Appetit December 2008

- 5 tablespoons olive oil, divided
- 2 1/2 pounds medium Yukon Gold potatoes, peeled, cut lengthwise into 1/8-inch-thick slices
- 1 1/2 teaspoons coarse kosher salt plus additional for mushrooms
- 3/4 teaspoon freshly ground black pepper plus additional for mushrooms
- 1 1/4 cups (or more) heavy whipping cream, divided
- 1 cup freshly grated Parmesan cheese (about 3 ounces), divided
- 2 tablespoons chopped fresh thyme
- 6 garlic cloves, thinly sliced
- 12 ounces fresh crimini (baby bella) mushrooms, sliced

Preheat oven to 375°F. Brush 13x9x2-inch glass or oval ceramic baking dish with 2 tablespoons oil. Arrange 1/3 of potatoes, slightly overlapping, in dish. Sprinkle with 1/2 teaspoon coarse salt and 1/4 teaspoon pepper. Pour 1/3 cup cream over; sprinkle with 1/4 cup cheese. Repeat layering 1/3 of potatoes, 1/2 teaspoon salt, 1/4 teaspoon pepper, 1/3 cup cream, and 1/4 cup cheese 2 more times. Bake uncovered until potatoes are tender, adding cream by tablespoonfuls if dry, about 45 minutes. Remove from oven; maintain oven temperature.

Sprinkle thyme and garlic slices over gratin. Toss mushrooms in medium bowl with 3 tablespoons oil; sprinkle with coarse salt and pepper. Arrange mushroom slices atop gratin around edge of dish. Drizzle with 1/4 cup cream; sprinkle with 1/4 cup cheese. Continue to bake uncovered until mushrooms are tender and potato edges are golden brown, about 20 minutes longer. DO AHEAD: Can be made 1 day ahead. Cool 1 hour in dish; cover and chill. Before serving, cut gratin into 10 pieces. Transfer to rimmed baking sheet. Cover with foil and rewarm in 350°F oven, 10 to 15 minutes.