Serves 8 to 10

- Softened butter or nonstick cooking spray for dish

- 3 large parsnips

- 3 smaller sweet potatoes

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- 4 medium Yukon gold potatoes

- 1 tablespoon coarse sea salt or kosher salt

- 1-¼ teaspoons fine sea salt or table salt

- 1 teaspoon freshly ground black pepper

- ½ cup half-and-half

- ½ cup whole milk

- 3 tablespoons unsalted butter, divided

- 4 tablespoons minced Italian parsley, divided

- ¼ cup finely grated Parmesan cheese

- 1/3 cup finely grated Gruyere cheese

1. Lightly butter or spray a 2-quart gratin or broiler-safe casserole dish and set aside.

2. Peel the parsnips, sweet potatoes and Yukon gold potatoes; cut into 3/4-inch cubes. Put vegetables into a stockpot or similar large pan and cover with water by about 4 inches. Add coarse salt. Bring to a boil over high heat, reduce heat to medium and cook, uncovered, about 30 to 35 minutes or until vegetables are tender when pierced with the tines of a fork. Drain well and transfer to a large bowl. Sprinkle with fine salt and pepper, turning several times.

3. Preheat oven to 350 degrees. In a saucepan over medium heat, combine half-and-half, milk and 2 tablespoons butter. When hot and the butter has melted, pour half over the vegetables and mash coarsely with a potato masher. When liquid has been absorbed, add the remaining liquid with 3 tablespoons parsley. Mash coarsely again until well blended.

4. Spoon into the prepared baking dish, smoothing the top. Combine cheeses and sprinkle over top. Cut remaining tablespoon butter into small bits and dot the top. (The dish can be made 24 hours in advance, covered and refrigerated. Remove from refrigerator 30 minutes before baking.) Bake 25 minutes or until heated through. Preheat broiler and broil until top is golden, about 3 to 4 minutes. Sprinkle with 1 tablespoon parsley and serve hot.

From “Williams-Sonoma Christmas Entertaining”