Cheesy Sweet Potato Gratin Recipe - Fork Knife Swoon (2024)

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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. Vegetarian and gluten free.

Cheesy Sweet Potato Gratin Recipe - Fork Knife Swoon (1)

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.

Cheesy Sweet Potato Gratin Recipe - Fork Knife Swoon (2)

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

This rich and cheesy sweet potato gratin combines mostly simple pantry ingredients with a couple of seasonal additions. Here’s what you’ll need to make it:

  • sweet potatoes: of course! We’ll use vibrant sweet potatoes in place of traditional yellow potatoes. For the best texture, be sure to slice them very thin, no more than 1/8” thick.
  • cheese: a blend of gruyére, sharp cheddar, and parmesan cheeses add tons of flavor, lots of creamy goodness, and forms the gratin or “crust” of the dish as it bakes.
  • olive oil and garlic: the flavorful base of the creamy sauce.
  • cream: for a rich and fully indulgent sauce that binds the scalloped sweet potatoes together.
  • thyme and nutmeg: for cozy, earthy fall flavor.
  • salt and pepper: be sure to season to taste!

Find all the exact measurements and full recipe instructions below.

Admittedly, slicing the potatoes takes a little bit of time (a mandoline is quite helpful for this), but after that, things come together quickly, and the gratin emerges from the oven golden and glorious and worth every ounce of effort. Happy cooking!!

Cheesy Sweet Potato Gratin Recipe - Fork Knife Swoon (3)

Other cozy comfort foods to cook next:

  • Simple homemade chicken ramen
  • Lemony kale and white bean soup
  • Pasta with broccoli and chicken sausage
  • Butternut squash noodle soup
  • Spinach and ricotta stuffed shells

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


Cheesy Sweet Potato Gratin Recipe - Fork Knife Swoon (4)

Sweet Potato Gratin

★★★★★4.9 from 8 reviews

  • Author: Laura Bolton – Fork Knife Swoon
  • Prep Time: 20 mins
  • Cook Time: 50 mins
  • Total Time: 1 hour 10 minutes
  • Yield: 46 Servings 1x
  • Category: Side Dish, Savory, Dinner, Holiday
  • Method: Baking
  • Cuisine: American, French
  • Diet: Vegetarian
Print Recipe


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
  • 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


  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.
  8. 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

Originally published on December 11, 2012. Updated photos by Jenn Davis added November 2018.

posted by Laura on December 11, 2012 (last updated July 16, 2022)

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38 comments on “Sweet Potato Gratin”

  1. Mary Workman Reply

    Any other cheesss besides Gruyere, family is not a fan!

    • Laura Reply

      Hi, Mary! I might try gouda, or just go with all sharp cheddar. Enjoy!!

  2. Christine Balascoe Reply

    Can this be made with Yams instead of sweet potatoes?

    • Laura Reply

      Hi, Christine! I haven’t tried using yams, but I would think they should work. They are starchier than sweet potatoes, so the baking time may vary slightly. They key is to slice them super thin, and then just bake until bubbly and fork tender. Enjoy!!

  3. Donna Reply

    I was wondering if this recipe could be made ahead and frozen for a short time then thawed and reheated?

    • Laura Reply

      Hi, Donna! I haven’t tried freezing these potatoes. Generally, scalloped potatoes are okay to freeze but I don’t want to steer you wrong! However, you can definitely make them a couple of days in advance, cover tightly and refrigerate, and then reheat in the oven when ready to serve. Enjoy!!

      • Donna Reply

        Thank you. I think I will make a day or two ahead. I may try freezing a small portion just to test it out!

        • Laura Reply

          Thanks, Donna! Please let me know how it turns out! 🙂

  4. Rachel Reply

    Does the recipe call for 0.5 Cups of Heavy Cream or 1.5 Cups if making the single recipe?

    • Laura Reply

      Hi, Rachel! For the standard recipe you’ll need 1.5 cups. Enjoy!!

  5. Margaret Reply

    Can I use cream hcheese along with the heavy cream

    • Laura Reply

      Hi, Margaret! I haven’t tried adding cream cheese so I’m not sure exactly how it would turn out. That would definitely make it super rich! Please let me know your results 🙂 Enjoy!

  6. PJ Reply

    Can’t wait to try this with the locally-grown sweet potatoes I just got, and the thyme from my garden (the only herb I seem to be able to grow). My kids, their SA’s, and my grandson are all foodies, so they will be good taste-testers. Thanks!

    • Laura Reply

      Enjoy! Thanks, PJ!

  7. Kristy Reply

    Smash hit of Christmas lunch. Fabulous sweet potato recipe. Decadent and delicious.

    • Laura Reply

      Oh, yay! Thanks so much, Kristy!!

  8. Kate Reply

    Hi! Can I make this. A day ahead and not bake it? Or would you suggest I bake it and reheat the next day?

    • Laura Reply

      Hi Kate! I haven’t tried making it in advance without baking, but you can definitely bake it and reheat the next day. I would reheat at 350℉ covered with foil until it’s warmed through then uncovered for the last few minutes. Enjoy!!

  9. Michelle Reply

    This looks so delicious! Question – if I double the recipe, would you suggest I make it in 2 separate 9 in baking dishes, or should I combine it into a larger dish?

    • Laura Reply

      Hi Michelle! So you definitely can make it in two separate dishes. I worry a little about the potatoes cooking evenly in a larger dish (I haven’t tested it). I would try a 9×13 and be ready to cover with foil and/or turn the oven down (350℉?) for the second half of baking/cook for slightly longer in case the top starts browning before the potatoes are fully cooked through. Enjoy!!

  10. Amy Reply

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

    • Laura Reply

      Thanks so much, Amy!!

  11. Helen Reply

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

    • Laura Reply

      Thank you so much, Helen!!

  12. Amy Westerman Reply

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

    • Laura Reply

      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!!

  13. Janace Reply

    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!

    • Laura Reply

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

  14. Karla Reply

    What size Casserole dish would be suitable for this dish?

    • Laura Reply

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

  15. Brandi Reply

    So yummy!

    • Laura Reply

      Thanks, Brandi!!

  16. Tamie Reply

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

    • Laura Reply

      Thanks so much, Tamie! Happy Thanksgiving!!

  17. Stacy Reply

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

    • Laura Reply

      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…

  18. Erica Reply

    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!

    • Laura Reply

      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…

Leave a comment »

Cheesy Sweet Potato Gratin Recipe - Fork Knife Swoon (2024)


Do you stab sweet potatoes before baking? ›

Before baking, use a fork to prick each sweet potato several times. You don't need to jab the fork in deep. We're creating steam vents. Otherwise the pressure in the sweet potato could build up so high in the oven that it explodes—an unlikely possibility but one best avoided!

How do you know when a sweet potato casserole is done? ›

Sprinkle the topping evenly over the sweet potato mixture, then pop it into the oven and let it bake for 40 to 45 minutes. You will know it's done when the topping is lightly browned and the center of your casserole is set and firm.

How do you make sweet potato casserole not watery? ›

Eggs and cream help stabilize the dish and prevent it from becoming too runny (a common complaint with many sweet potato casserole recipes). Make it as smooth or chunky as you like!

Why put egg in sweet potato casserole? ›

The egg is the all-important binder in a sweet potato casserole: it enriches and stiffens the mixture without making it heavy. Make sure to cool the mash slightly before adding the egg so it doesn't scramble, and to stir well so there are no streaks of cooked egg white in the finished dish.

What happens if you don't stab a potato before baking it? ›

A: I would just skip poking the potato all together. It is very rare that a baked potato will burst if the steam can't escape.

What happens if you don't stab a baked potato? ›

It's up to you. Pricking potatoes with a fork prior to cooking supposedly prevents steam from building up inside them as they bake, which can make them explode in the oven. However, this theory is highly debatable. I don't prick my potatoes, and in all my years of cooking, I have never had one explode in the oven.

Why is my sweet potato still hard after baking? ›

The reason they are hard in the middle is cook them longer or on a higher temperature. Soaking will not help soften your sweet potato unless you are putting the potato and water in a pot on the stove and cooking it. If your sweet potato is still hard it's not cooked enough.

Can you prep sweet potatoes ahead of time? ›

Potatoes: Peel or pare and chop up to a day in advance. Store in a bowl of cold water in the refrigerator. Sweet potatoes: Peel and chop 3 to 4 days in advance. Store in a sealed bag or container with an airtight lid in the refrigerator.

Can you overcook a sweet potato? ›

Mushy Texture: Sweet potatoes contain a lot of moisture, and overcooking can cause them to become mushy and overly soft. Instead of a firm and slightly tender texture, they may turn into a puree-like consistency. Loss of Flavor: Overcooking can lead to a loss of flavor in sweet potatoes.

What is the sticky liquid from sweet potato? ›

The ooze is actually referred to as "sap." It is made up of sugar and starch combined with the moisture found in the vegetable, and it escapes out of the damage made from the knife. The sap really equals the sweetness. If it's pouring out of your potato, that means it's a sweet and delicious vegetable.

Why is boiling not good for sweet potatoes? ›

Bake, don't boil

Baking sweet potatoes caramelizes their natural sugars, especially when done whole. It intensifies their flavor and creates a richer taste compared to boiling, which can result in a watered-down, bland flavor.

Why do you soak sweet potatoes before baking? ›

The cold water bath helps rinse the starch off the sweet potatoes so they're a bit more crispy. That said, if you do not have the time, you can still get crispy baked sweet potato fries by using high heat and a little drizzle of olive oil.

Can I leave eggs out of sweet potato casserole? ›

Eggs (or not!)

– I've made this sweet potato casserole with and without eggs, both ways are delicious. The eggs act as a binder and gives the casserole a light and fluffy texture. Without eggs, the casserole doesn't have as much structure but it still silky smooth and tastes delicious.

How can I thicken my sweet potato casserole? ›

Add more potato and no liquid also you could use potato flakes to thicken them to the texture you like. Either with plain(all purpose) flour or cornflour mixed in milk to disolve first themn poured in ( not too much liquid just enough to disolve the powder).

Should you puncture potatoes before baking? ›

"Yes, it's good to prick them," Smith told Food52. "It pokes holes in the skin, which allows steam to escape. Otherwise, they could explode—it doesn't happen all the time, but it happens every once in a while. The potato is full of water it's trying to turn to steam, or water vapor.

Do you pierce a potato before baking in the oven? ›

Yes … poking holes in the skin of a potato keeps it from splitting open and squealing in the oven [or microwave.] It's weird, but true, they will actually whistle on the baking dish or tray from the water escaping through the skin, so poke it all over with a fork for even cooking.

Do you have to pierce potatoes before roasting? ›

For this experiment, we washed two potatoes and poked holes with a fork in one of them, leaving the other unpoked. The potatoes were then placed in the oven at 400 degrees Fahrenheit, and they each took one hour to fully bake. Overall, we did not detect any difference between the poked and unpoked potatoes.

Should sweet potatoes be soaked before baking? ›

TIPS & TRICKS to Make this Recipe: The main secrets to achieving that incredible crispy texture, is to soak the cut sweet potatoes in cold water for at least 30 minutes. This helps remove the starch from the sweet potatoes so they´re not limp & soggy.

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