Serves
Makes 6 to 8 servings
Ingredients
- 2½ cups whole milk
- 1 ½ cups heavy cream
- 2 teaspoons Kosher salt
- 2 teaspoons fresh thyme, minced
- 1 clove garlic, grated or finely chopped
- 1/8 teaspoon freshly ground black pepper
- 2 pounds Yukon Gold potatoes, peeled and sliced ¼ inch thick
- 1 pound sweet potatoes, peeled and sliced ¼ inch thick
- 1 pound large parsnips, peeled and sliced ¼ inch thick
- ½ teaspoons unsalted butter, softened
- ½ cup shredded Gruyère cheese
- ½ cup shredded white Cheddar cheese
- ½ cup grated Parmigiano-Reggiano cheese
Procedure
Sweet potatoes and parsnips add a subtle sweetness to this classic gratin. Use a mandolin to slice the root vegetables with precision. This will help the dish cook more evenly. The addition of three different cheeses creates a unique layering of flavors and textures.
Preheat the oven to 400°F. Rub the butter over the bottom and sides of a 2-quart gratin dish.
In a large heavy pan, combine the milk, cream, salt, thyme, garlic and pepper. Place over medium heat and stir for 3 minutes, or until small bubbles appear around the edges of the pan. Add the Yukon Gold potatoes, sweet potatoes and parsnips. Stir to coat and simmer gently, uncovered, for 10 to 12 minutes, until the potatoes are partially cooked. Remove from the heat.
Use a slotted spoon to transfer half the vegetables to the gratin dish. Sprinkle with half each of the Gruyère, cheddar, and Parmigiano-Reggiano cheeses. Add the remaining vegetables. Use two forks to arrange the top layer of potatoes in a slightly overlapping design, evenly distributing the different-colored potatoes. Ladle the hot cream mixture over the vegetables and sprinkle with all of the remaining cheeses.
Bake for 35 minutes, or until the potatoes are tender when pierced with a skewer or the tip of a knife and the gratin is bubbling and golden.
Let the gratin rest for 10 minutes before serving.
