This sweet potato gratin with mushrooms is an easy indulgence

This isn't everyday food - it's extravagance. Simple, and not too expensive, the gratin works as a main course or side dish. It might even be nice as a side.

Sweet Potato and Mushroom Gratin

Servings: 4

Active time: 20 minutes | Total time: 50 minutes

Creamy and rich, this sweet potato gratin makes a hearty side - but can also act as a main course, served with a green salad dressed in a pungent vinaigrette on the side.

If you can't have onion, skip it.

No sweet potatoes? This would work with thinly sliced squash or other types of potatoes.

Out of Parmesan? Use another hard, meltable cheese such as Gruyere or cheddar.

Storage Notes: Refrigerate for up to 4 days or freeze, wrapped airtight, for 1 month.

INGREDIENTS

• 2 tablespoons unsalted butter

• 1/4 small yellow onion (1 ounce), sliced (optional)

• 6 ounces small mushrooms (any kind), sliced

• 1/4 teaspoon fine salt, plus more as needed

• 1 3/4 cups heavy cream, divided

• 3/4 cup (3 ounces) grated Parmesan cheese, divided

• 2 large sweet potatoes (1 1/2 pounds total), peeled and thinly sliced

• 1 sprig fresh thyme, plus a few fresh thyme leaves for garnish (optional)

DIRECTIONS

Position a rack in the middle of the oven and preheat to 400 degrees.

In a large skillet over medium-high heat, melt the butter. When it begins to sizzle, add the onion, if using, mushrooms and salt. Cook, stirring occasionally, until the mushrooms release their liquid and begin to brown, about 5 minutes. Add about 1/2 cup of the heavy cream, using it to help you scrape up any browned bits from the bottom of the pan. Add the remaining cream and quickly stir in about half of the cheese. Nestle the sweet potatoes in with the mushrooms, fitting them into a flat layer, and add the sprig of thyme, if using. Bring to a boil. Remove from the heat, cover the skillet tightly with aluminum foil and transfer to the oven.

Roast for 25 minutes, then remove the foil and top with the remaining cheese. Continue roasting, uncovered, for another 10 to 15 minutes, or just until the potatoes are tender. Garnish with thyme leaves, if using, and serve hot, family-style.