Sweet Potato Gratin

In this simple, cheesy sweet potato gratin recipe, sweet potatoes, gruyere, cheddar, garlicky cream, and fresh thyme come together to create a delicious twist on the classic potato au gratin casserole.

sweet potato gratin via forkknifeswoon.com

A cheesy sweet potato gratin

I would almost always choose sweet potatoes over regular potatoes, and this sweet potato gratin – a vibrant, seasonal twist on the classic potatoes au gratin casserole – is no exception.

It’s a simple recipe: layers of sliced sweet potatoes baked until bubbly in a garlicky cream sauce with a triple dose of cheesy goodness and fresh herbs; at its heart cozy comfort food that’s perfect for holiday entertaining and sure to become a seasonal favorite.

sweet potato gratin via forkknifeswoon.com

Here’s what you’ll need to make this gratin

  • sweet potatoes
  • gruyére, sharp cheddar, and parmesan cheeses
  • olive oil
  • garlic
  • cream
  • thyme
  • nutmeg
  • salt and pepper

Find all the exact measurements and full recipe instructions below.

sweet potato gratin via forkknifeswoon.com

Other cozy comfort foods to cook next:

If you make this sweet potato gratin recipe, be sure to tag me on Instagram with the hashtag #forkknifeswoon and leave a comment and rating below letting me know how you liked it! ★★★★★ Star ratings are especially helpful because they help others find my recipes too. xo, Laura

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sweet potato gratin via forkknifeswoon.com

Sweet Potato Gratin


Description

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.


Ingredients

Scale
  • 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
  • 11/2 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

Instructions

  1. Preheat the oven to 375℉. Lightly grease a 9-inch baking dish with butter or nonstick baking spray. Set aside.
  2. 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.
  3. 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.
  4. 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.
  5. 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.
  6. 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.
  7. 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!!
  • Category: Side Dish, Savory, Dinner, Holiday
  • Method: Baking
  • Cuisine: American, French

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

Originally published on December 11, 2012. Updated recipe photos by Jenn Davis, of the lovely baking blog Two Cups Flour added November 2018.

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18 Comments

  1. 12.26.20
    Amy said:

    This recipe is delicious. We scrapped the pan. I substituted sage instead of thyme. Really, really good.

    • 12.27.20
      Laura said:

      Thanks so much, Amy!!

  2. 11.27.20
    Helen said:

    Excellent. Followed recipe exactly using half-and-half instead of heavy cream. Don’t omit the fresh thyme. Wonderful flavors.

    • 11.27.20
      Laura said:

      Thank you so much, Helen!!

  3. 11.27.19
    Amy Westerman said:

    I love this recipe and have made it a few times. Is it something that can be made a day ahead?????

    • 11.27.19
      Laura said:

      Hi Amy! So happy you love the recipe! Yes, you can make it the day before (or morning of), and reheat in the oven when ready to serve. Happy Thanksgiving!!

  4. 11.17.19
    Janace said:

    I made this for a potluck at my church today and I got a ton of compliments! I think I’ll probably make it for Thanksgiving dinner this year as well. Thanks for the great recipe, love the blog!

    • 11.17.19
      Laura said:

      This is one of our favorites for Thanksgiving too 🙂 Thanks, Janace!

  5. 8.13.18
    Karla said:

    What size Casserole dish would be suitable for this dish?

    • 8.14.18
      Laura said:

      Hi Karla! I’d recommend a 9-inch square or oval baking dish for this gratin. Enjoy!

  6. 11.18.17
    Brandi said:

    So yummy!

  7. 11.24.16
    Tamie said:

    This gratin is specially requested by family and friends for the past 3 years. It is absolutely delicious!

    • 11.24.16
      Laura said:

      Thanks so much, Tamie! Happy Thanksgiving!!

  8. 11.27.13
    Stacy said:

    Made this tonight for Thanksgiving. It looks and taste great!! I will serve it tomorrow

    • 12.2.13
      Laura said:

      Thank you so much, Stacy! So glad you enjoyed the recipe! It’s one of my favorite dishes to serve for guests at the holidays…

  9. 4.12.13
    Erica said:

    I don’t know what I did wrong, but mine turned into a groopy, oily mess. The cheese didn’t melt despite bubbling like crazy, and there was this oily goo through the whole dish. Bummer, because I was hoping to love this recipe!

    • 4.28.13
      Laura said:

      Erica, I am so sorry to hear that! I’ve made this recipe many times without anything like that happening… usually the cheese begins to melt even as I pour the warm cream mixture over the sweet potato layers. My only thought it that it could possibly be an issue with the specific brand(s) of cheese used? Alternatively, you could try melting the cheese completely in the cream mixture while it is on the stove, and then pouring that over the layered potatoes…

Hi! I'm Laura, the food-obsessed cook, writer, and photographer behind Fork Knife Swoon, where you'll find mostly sweet, seasonal recipes and stories from my Northern Virginia kitchen.

All photography and content copyright Laura Bolton ©2021, and may not be used without permission.