What could be better than a rich and creamy bowl of mashed potatoes? How about a bowl of mashed potatoes infused with celery and horseradish?

This fluffy bowl piles on the roots, with celery root and horseradish joining the mix. The result is a delicious side of potatoes, with an extra dimension of fragrance, flavor and bite.

Celery root, also known as celeriac, is the dark horse of root vegetables. Don’t let its gnarly, bulbous exterior put you off. Once you cut away the skin, a milky white interior is revealed, softly redolent with celery. Celery root can be eaten raw and grated into salads, and when cooked, it’s a non-starchy alternative or complement to potatoes in mashes, gratins and soups.

Horseradish is also a root and belongs to the mustard family, which explains its peppery bite.

Horseradish is often grated raw and folded into sauces and garnished over meats. Sharp and nutty, horseradish is quite strong when fresh, but its flavor fades and bite softens with cooking, so don’t be deterred by the amount in the recipe.

This is a lovely side dish to accompany meat and stews. The potatoes are left unpeeled, and their nutrient-rich skins fleck this side dish, adding flavor and texture. Peel the potatoes if you prefer a smoother texture.

Mashed Potatoes and Roots

Active Time: 10 minutes

Total Time: 55 minutes

Yield: Serves 6 to 8

1 1/2 pounds Yukon gold potatoes, cut into 1-inch pieces

1 1/2 pounds celery root, peeled, cut into 1-inch pieces

1 bay leaf

3 thyme sprigs

Salt

1/4 cup unsalted butter, softened

1/2 cup sour cream, plus more as needed

4 tablespoons finely grated Parmigiano-Reggiano cheese, divided

3 tablespoons finely grated peeled fresh horseradish, divided

1/2 teaspoon pepper

Preheat the oven to 350 degrees.

Combine the potatoes and celery root in large pot and cover with cold water. Tie the bay leaf and thyme sprigs with kitchen string to make a bouquet garni and add to the pot along with 1 tablespoon salt.

Bring to a boil and simmer, partially covered, until the potatoes and celery root are very tender, about 20 minutes. Drain thoroughly and discard the bouquet garni.

Transfer the vegetables to a large bowl, add the butter, and mash with a potato masher. Stir in the sour cream, 2 tablespoons cheese, 2 tablespoons horseradish and the pepper. If too thick, mix in more sour cream to your desired consistency. Add salt to your taste and mix well. Transfer the potatoes to a buttered 2-quart baking dish.

Mix the remaining 2 tablespoons cheese and 1 tablespoon horseradish in a small bowl. Sprinkle over top of potatoes. Transfer the potatoes to the oven and bake until the top is tinged golden brown and the potatoes are heated through, about 25 minutes. Serve warm.