Sweet Potato Au Gratin

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Last Updated on March 25, 2024 by Share My Kitchen

This simple sweet potato au gratin recipe is easy and delicious. It combines sweet potatoes, cheddar, garlicky crème, gruyere, and fresh thyme to make a tasty twist on the classic potato au gratin. This is vegetarian and gluten-free.

Cheesy Sweet Potato Au Gratin

Sweet potatoes are one of the best types of potatoes, and it is almost always preferable to use sweet potatoes rather than regular potatoes. This sweet potato gratin, a seasonal, vibrant twist on the traditional potato au gratin casserole, is not an exception.

This is a simple recipe. It is just layers of sweet potatoes that are baked until they become bubbly in a garlicky cream sauce with fresh herbs and a triple dose of cheese. It’s definitely cozy comfort food, so it’s perfect for holiday entertaining. It is sure to become a seasonal favorite.

What You Need to Make This Sweet Potato Au Gratin

This sweet potato au gratin is rich and creamy. It combines simple pantry ingredients with a few seasonal additions. Here are the ingredients you will need to make it:

  • Sweet potatoes: Of course! You will need vibrant sweet potatoes instead of yellow potatoes. To get the best texture, slice them thinly, not more than 1/8″.
  • Cheese: A mixture of sharp cheddar, gruyere, and parmesan cheeses gives the dish its flavor, creamy texture, and it forms the “crust” or gratin as the dish bakes.
  • Olive oil and garlic: The flavorful base for the creamy sauce.
  • Cream: You need this to get a rich and indulgent sauce, which binds the scalloped potatoes together.
  • Thyme and nutmeg: For a warm, earthy autumn flavor.
  • Salt and pepper: Season to your liking!

Below are the exact measurements as well as full instructions for making this recipe.

Although it is time-consuming, the process of slicing potatoes can be done quickly. You can use a mandoline for this. However, once you have done that, the gratin comes together quickly, and it emerges from the oven looking golden and beautiful. It’s well worth the effort. Enjoy your cooking!

Sweet Potato Au Gratin Recipe Card

Prep Time20 minutes
Cook Time50 minutes
Total Time1 hour and 10 minutes
Yield4 to 6


  • Mandoline
  • all-clad weeknight pan
  • extra-virgin olive oil


  • 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


  1. Preheat the oven to 375°F. Use butter or a nonstick spray to lightly grease a 9-inch baking pan. Set aside.
  2. Use a mandoline to carefully cut the sweet potatoes horizontally into thin rounds, no more than 1/8″ thick. In the baking dish, place the sweet potato slices in one layer in an overlapping pattern.
  3. Reserve 1/2 cup of Gruyere cheese. Then, sprinkle the sweet potatoes generously with the remaining Gruyere, cheddar, and Parmesan cheeses. Repeat this step with two more layers of potatoes and cheese.
  4. Meanwhile, make sure to heat the olive oil in a saucepan over medium heat until it shimmers. Stir in the garlic, and cook until it’s golden and fragrant, stirring frequently for approximately 5 minutes.
  5. Then, add the cream, nutmeg, and thyme. Bring to a simmer. Cook, stirring occasionally, until it is slightly thickened, for approximately 5 minutes. Next, season with salt and pepper to taste. Don’t let it come to a boil.
  6. Mix in the 1/2 cup of Gruyere cheese you reserved, until it’s melted. Slowly pour the warm cream mixture on top of the sweet potatoes, and let it settle in between the layers. Add a few fresh thyme leaves to finish.
  7. Bake for 45-50 minutes, or until the gratin are golden brown and bubbly and the potatoes are tender. Cover the gratin loosely with aluminum foil if it begins to brown too fast.
  8. Take it out from the oven and let it cool for about 10-15 minutes before serving. Then, add more fresh thyme to garnish. Enjoy!

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