Sweet Potato and Leek Gratin with Gruyère Cheese

Ingredients

• 3 pounds sweet potatoes, peeled and thinly sliced
• 2 leeks, white and light green parts, halved and thinly sliced
• 3 tablespoons unsalted butter
• 1 1/2 cups heavy cream
• 1/2 cup whole milk
• 3 cloves garlic, minced
• 1/4 teaspoon ground nutmeg
• 1 teaspoon kosher salt
• 1/2 teaspoon black pepper
• 8 ounces Gruyère cheese, shredded
• 1/4 cup grated Parmesan cheese
• 1 tablespoon fresh thyme leaves

Method

1. 1

   Preheat the oven to 375°F. Butter a 9x13-inch baking dish.

2. 2

   Melt the butter in a 9-inch skillet over medium heat. Add the leeks and cook, stirring occasionally, until softened and lightly golden, about 8 minutes.

   8:00 · Cook leeks
3. 3

   Add the garlic to the leeks and cook, stirring, until fragrant, about 1 minute. Remove from heat.

   1:00 · Cook garlic
4. 4

   In a bowl, whisk together the heavy cream, milk, nutmeg, salt, and pepper.

5. 5

   Arrange one-third of the sweet potato slices in an overlapping layer in the prepared baking dish. Scatter half of the leek mixture over the potatoes, then sprinkle with one-third of the Gruyère.

6. 6

   Repeat with another layer of sweet potatoes, the remaining leeks, and another third of the Gruyère. Top with the final layer of sweet potatoes.

7. 7

   Pour the cream mixture evenly over the layered potatoes, pressing down gently so the liquid settles between the layers.

8. 8

   Cover the dish tightly with foil and bake until the sweet potatoes are tender when pierced with a knife, about 50 minutes.

   50:00 · Bake covered
9. 9

   Remove the foil, sprinkle the remaining Gruyère and the Parmesan over the top, and bake uncovered until golden and bubbling, about 20 minutes.

   20:00 · Bake uncovered
10. 10

    Let the gratin rest for 10 minutes before scattering with fresh thyme and serving.

    10:00 · Rest before serving