Thanksgiving Sweet Potato Gratin

Sweet potatoes layered with cheese and a herby cream sauce, baked until golden brown and bubbly.

By Delish

Original recipe source

Cook time: 120 minutes

Servings: 12

Ingredients

• 1 tablespoon unsalted butter
• 2 tablespoons unsalted butter
• 4 teaspoons cloves garlic
• 2 tablespoons fresh thyme leaves
• 1 tablespoon fresh sage leaves
• 0.5 teaspoon kosher salt
• 1 cup heavy cream
• 0.75 cup whole milk
• 0.25 teaspoon ground cinnamon
• 0.25 teaspoon ground nutmeg
• 2 large eggs
• 0.5 cup grated Parmesan
• 1 to taste freshly ground black pepper
• 2 lb sweet potatoes
• 1 pinch kosher salt
• 0.67 cup shredded Gruyère cheese
• 0.25 cup grated Parmesan
• 1 as needed unsalted butter
• 1 as needed fresh thyme leaves

Instructions

1. Preheat oven to 375°. Butter a 2-quart casserole or gratin dish with 1 tablespoon butter.
2. In a small saucepan over medium heat, melt 2 tablespoons butter. When butter stops foaming, add garlic and cook, stirring, until fragrant, about 30 seconds.
3. Add thyme, sage, and 1/2 teaspoon salt and cook, stirring occasionally, until heated through, about 30 seconds.
4. Add cream, milk, cinnamon, and nutmeg. Bring to a simmer (do not let boil) and cook, stirring occasionally, until slightly thickened, about 5 minutes. Remove from heat.
5. In a medium bowl, beat eggs. Transfer 1 cup cream mixture to a liquid measuring cup or bowl with a spout. Whisking constantly, slowly stream cream mixture into eggs a few tablespoons at a time until incorporated.
6. Add egg mixture to saucepan with remaining cream mixture and whisk until combined. Whisk in 1/2 cup Parmesan; season with pepper.
7. Line bottom of prepared dish with a layer of potatoes, slightly overlapping slices; season with a pinch of salt. Top with 2/3 cup Gruyère and 2/3 cup cream mixture.
8. Repeat 3 times, ending with cream mixture. Top final layer with remaining 1/4 cup Parmesan.
9. Butter a piece of foil and tightly cover dish. Bake gratin 30 minutes, uncover, and continue to bake until sides are bubbling and golden brown, about 30 minutes more.
10. Top with thyme.