In this simple, cheesy sweet potato gratin, sweet potatoes, gruyere, cheddar, garlicky cream, and fresh thyme come together to create a delicious twist on the classic potato casserole.
- 2 lbs sweet potatoes, peeled
- 1 cup grated Gruyére cheese
- 1/2 cup grated sharp cheddar cheese
- 1/4 cup grated Parmesan cheese
- 1 tsp olive oil
- 1 Tbsp fresh garlic, finely minced
- 1–1/2 cups heavy cream or half-and-half
- 4 sprigs fresh thyme, removed from stems and finely chopped
- 1/2 tsp ground nutmeg
- Kosher salt and freshly-ground black pepper, to taste
- Preheat the oven to 375℉. Lightly grease a 9-inch baking dish with butter or nonstick baking spray. Set aside.
- Using a mandoline, carefully slice the sweet potatoes horizontally into thin rounds, no larger than 1/8” thick. Place the sweet potato slices in a single layer in an overlapping pattern in the baking dish.
- Set aside 1/2 cup of Gruyére cheese. Sprinkle the sweet potatoes with a third of the remaining Gruyére, cheddar, and Parmesan cheeses. Repeat with two more layers of potatoes and cheese.
- Meanwhile, heat the olive oil to a medium sauce pan over medium heat until shimmering. Add the garlic, and cook, stirring occasionally, until golden and fragrant, about 5 minutes.
- Add the cream, nutmeg, and thyme, and bring to a simmer. Cook, stirring often, until slightly thickened, about 5 minutes. Season with salt and pepper, to taste. Do not let come to a boil.
- Stir in the reserved 1/2 cup of Gruyére cheese, until melted. Slowly pour the warm cream mixture over the sweet potoates, letting it sink in amongst the layers. Top with a bit of fresh thyme leaves.
- Bake until the gratin is golden brown and bubbly and the potatoes are tender, about 45-50 minutes. If the gratin begins to brown too quickly, cover loosely with aluminum foil, as needed.
- Remove from the oven and let rest for 10-15 minutes before serving. Garnish with more fresh thyme. Enjoy!!
Keywords: sweet potato gratin, sweet potato casserole, potato gratin, garlic and thyme, gruyere cheese, sweet potato gratin with gruyere, au gratin, sweet potatoes, vegetarian, gluten free