Root vegetables are available year round, but their peak season is smack in the middle of winter. This is good news for vegetable fans who want to stay healthy in cold weather. Rutabaga, sweet potatoes, parsnips and celery root are deeply flavorful, sweet, and packed with vitamins, nutrients and fiber; after all, as storehouses of natural sugars, they’re the vital roots of growing plants. All of which translates to wholesome satisfaction on the dinner plate. (Although who says you can’t mix them with a little cheese and cream?) Feel free to use your favorite root vegetables in this recipe. You will need about 3 pounds total.
2 cups sour cream
1 large garlic clove, minced
2 teaspoons minced fresh sage leaves
2 teaspoons chopped fresh thyme leaves
1 teaspoon salt
1/2 teaspoon freshly ground black pepper
1/4 teaspoon ground nutmeg
1-1/2 pounds medium Yukon Gold or red potatoes, unpeeled
1 large sweet potato, peeled, about 3/4 pound
1 medium rutabaga, peeled, about 3/4 pound
4 ounces Gruyère cheese, finely grated
1/3 cup heavy cream, or more as needed
1. Preheat the oven to 375F and butter an 8-by-10-inch gratin dish.
2. Whisk the sour cream, garlic, sage, thyme, salt, pepper and nutmeg in a bowl.
3. Thinly slice the vegetables, about 1/8 inch thick, preferably with a mandoline. Arrange half of the Yukon or red potatoes, overlapping in concentric circles, in the bottom of the gratin dish. Spread 1/2 cup of the sour cream over the potatoes and sprinkle with some of the Gruyère. Cover with a layer of the sweet potatoes, overlapping in concentric circles. Spread with 1/2 cup of the sour cream and some of the Gruyère. Repeat with the rutabaga, ½ cup more sour cream and the Gruyère. Finish with the remaining Yukon or red potatoes, sour cream and Gruyère. Drizzle the cream in and around the edges, corners and gaps in the gratin.
4. Cover the gratin with lightly buttered foil. Bake in the oven for 45 minutes. Remove the foil and continue to bake until the vegetables are tender when pierced with a knife and the top is golden brown, 15 to 25 minutes. Let stand for 5 to 10 minutes before serving.