Turnip-Celeriac Mashed Potatoes

Turnip-Celeriac Mashed Potatoes (Recipe adapted from Paula Deen's recipe)

6 medium to large potatoes, skin on
1-2 large turnips, peeled
and/or 1-2 bulbs celeriac
1/2 cup cream, heated
8 tablespoons (1 stick) butter, melted
1/2 cup sour cream
Salt and pepper

Slice potatoes and turnips and/or celeriac 1/4-inch thick. Cook in boiling water for 15 minutes or until fork-tender. Drain. Whip unpeeled cooked potatoes and turnips with electric mixer, mixing until moderately smooth (don't overbeat them; a few lumps are nice). Add hot cream, butter, and sour cream. Season with salt and pepper, to taste. Whip again until blended.