Sheet-Pan Root Vegetable Gratin
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Creamy, silky, and loaded with flavor, this Sheet Pan Root Vegetable Gratin is a feast for the eyes and palate. By cooking it on a sheet pan, every bite has that sought-after crispy edge, while underneath the gratin remains creamy and tender. Whether you're cooking for a holiday or a cozy family dinner, this easy gratin is a surefire hit!
Servings: 8 to 10
Ingredients
- 1 cup grated Gruyère
- 1 cup grated parmesan
- 1 Tablespoon butter, plus extra for greasing pan
- 1 medium shallot, diced
- 3 large garlic cloves, grated or minced
- 2 1/4 cups cream
- 1 ½ Tablespoons finely chopped rosemary (or thyme leaves)
- Kosher salt and pepper
- 1 1/2 pounds sweet potatoes, peeled (about 2-3 medium-long)
- 1 pound parsnips, peeled (about 4 large)
- 1 pound beets, peeled (about 4 medium)
- 2 Tablespoons chopped chives, optional for garnish
Instructions
- Preheat oven to 450ºF. Using soft butter, lightly grease the bottom and sides of an 18×13 sheet pan.
- Combine grated gruyere and grated parmesan in a medium bowl. Set aside.
- In a medium saucepan, melt butter over medium heat. Add shallot and garlic. Cook for 2 to 3 minutes until slightly softened. Add cream, chopped rosemary, 1 teaspoon salt and 1/2 teaspoon pepper. Over medium heat, bring to a simmer. Continue to simmer for 1 to 2 minutes, then remove from heat. Set aside while you prepare the vegetables.
- Using a mandoline or sharp knife, slice the peeled vegetables into rounds, ⅛-inch thick. TIP: Slice the beets last so your knife or mandolin doesn't stain the other veggies.
- Arrange one layer of vegetables on the buttered baking sheet, slightly overlapping the slices (use any pattern you'd like). Pour half the cream mixture over the vegetables, then sprinkle with a pinch of salt and a few grinds of black pepper to taste. Top with 3/4 cup of cheese mixture. Arrange another layer of vegetables and drizzle with remaining cream mixture.
- Cover the baking sheet with aluminum foil and bake for 20 minutes. Remove the foil and sprinkle top with remaining cheese mixture. Return tray to oven and bake until the vegetables and cheese are slightly browned and bubbling, for an additional 20 to 23 minutes.
- Let cool slightly, sprinkle with chopped chives, if using, and enjoy!
Notes
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- Slice the root vegetables evenly and thinly. You don’t want to slice the vegetables so thin that they will turn to mush. However, they need to be sliced quite thin or they will take too long to cook through. I like to aim for a uniform 1/8-inch thickness. A mandolin makes this job really easy and fast. I have, and love, this one.
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- Don't add too much cheese. Cheese adds delicious flavor to the gratin and also helps glue everything together. Just don't over do it with the cheese or the gratin could turn out greasy and too loose.
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- Cool slightly before serving. Allowing the gratin to cool slightly before serving will help the vegetables absorb more sauce and also make it easier to slice and serve.
- Make ahead: Arrange the first layer of vegetables on the sheet pan. Top with half the cream mixture and half the cheese mixture. Arrange the second layer of vegetables and do not add the other half of the cream or cheese. Top with foil and bake for 30 minutes. Remove foil and let cool. Once cooled, cover tightly with foil and refrigerate for up to 24 hours. When ready to serve, top the vegetables with remaining cream and cheese mixture and bake in a preheated 450ºF oven, uncovered, for 25 minutes, or until bubbly and golden.