Cheesy Sweet Potato Au Gratin with Gruyère (Make-Ahead)
Published Nov 06, 2023 Updated Oct 09, 2026
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This sweet potato au gratin is my savory, cheesy twist on the sweet potato dishes I grew up loving! We’re talking thin slices of sweet potato layered with a garlic cream sauce, fresh thyme, and three different cheeses: Gruyère, Gouda, and Parmesan. Yum!
Table of Contents
Author’s Note
A Cheesy Twist on A Classic Dish
If you love a classic sweet potato casserole with brown sugar pecans but you’re in the mood for something savory, this is the one to make. Don’t knock it till ya try it!
Let’s talk cheese, because this recipe uses THREE kinds! Gruyère is the main one (it’s the biggest amount by far), and it’s what gives you that melty, cheesy texture. A little Gouda makes the sauce extra creamy and helps it cling to every slice. I used smoked Gouda in my photos for a hint of smoky flavor, but regular Gouda works too. Then the Parmesan adds a salty, sharp flavor so the whole thing doesn’t taste too sweet. And y’all, all three melted together over sweet potatoes? So darn good!
And the best part is, you can put the whole thing together ahead of time and just pop it in the oven for about an hour when you’re ready. That is SUCH a lifesaver on busy holidays like Thanksgiving and Christmas!
Ingredient Notes
- Sweet potatoes: I used regular orange sweet potatoes for this one, and they’re the kind you want here. Japanese or white sweet potatoes are drier and starchier, so you’d end up with thicker, drier layers. Their natural sweetness under all that garlic and cheese is what makes this savory version so good!
- The garlic cream: It’s just butter, garlic, and heavy cream. The butter and garlic are what give you garlic flavor in every single layer. Stick with heavy cream, too! Half-and-half or milk can curdle during the long bake and leave you with a thin, watery sauce. (If you need it dairy-free, the swap is in the recipe notes.)
- Fresh thyme: It adds an herby flavor to all that rich cream and cheese. Plus, those little green flecks on top look so pretty when you pull it out of the oven!
How to Make Sweet Potato Au Gratin
This is what each step looks like, plus a few things to watch for along the way. (All the measurements and times are in the recipe card below!)
Prep the Sweet Potatoes, Cream, and Cheese
Step 1: Peel the sweet potatoes. Keep going until they’re smooth and bright orange all over. Peeling makes the slices softer once they’re baked!
Step 2: Slice them thin and even. Even slices are a big deal here! Uneven ones bake at different speeds, and thick ones can stay firm even after an hour in the oven. A mandoline gives you the most even slices, like these thin rounds. One reader found her mandoline a little tricky (she thought the blade wasn’t sharp enough), so if yours is dull, a sharp knife works too.
Step 3: Warm the garlic cream. Yours will look smooth and pourable, with little flecks of garlic and pepper all through it. Pouring it into a measuring cup with a spout, like this, makes it way easier to add just a little to each layer. One reader brought hers to a quick boil and said it still baked up great, so don’t panic if that happens. Just don’t let it keep boiling, or the dairy can separate and you’ll end up with a grainy sauce.
Step 4: Shred the cheese. Grating it by hand is worth it! You get these long, fluffy shreds and the creamiest melt. Bagged shredded cheese has a coating to keep it from clumping in the bag, and that coating keeps it from melting as smoothly.
Layer and Bake
Step 5: Start the first layer. This first layer covers the whole bottom of the dish, with the edges of the slices barely overlapping. If your sweet potatoes are still firm after baking, they were probably packed in too tight or sliced too thick.
Step 6: Coat each layer. You’ll add the cream first and the cheese on top, like this. Lightly coated, not drenched! You can still see a little orange around the edges, and that’s just right. If you pour on too much cream (don’t go overboard here!), the whole thing can turn out watery.
Step 7: Finish with the rest of the cheese. You’ll see cheese all over the top, with little flecks of thyme over the cream. Making it ahead? Stop right here, cover it, and pop it in the fridge (the timing is in the recipe notes).
Step 8: Cover it with foil. Here it is, sealed tight all the way around the rim and ready for the oven. The foil holds in the steam, which cooks the slices until they’re tender before the top has a chance to brown. When it’s done, the top will be golden with darker browned edges around the rim, just like the finished photos. I mean, look at that! Letting it rest before you scoop gives the sauce time to thicken up.
Mac’s Pro TipS
On the Holiday Table
This one is fancy enough for a holiday spread but totally at home next to the turkey, stuffing, and greens. For the greens, make my classic green bean casserole (with gluten-free option!). My maple glazed carrots are another easy side for the same table. And don’t forget my old-fashioned cornbread dressing with chicken, which takes stuffing to a whole new level.
Planning your Thanksgiving spread? Check out my Southern Thanksgiving Roundup with 75+ recipes!
More Holiday Side Dishes
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Cheesy Sweet Potato Au Gratin with Gruyère
Ingredients
- 3 large sweet potatoes (about 3 pounds, cut into 1/8 inch slices)
- 1 3/4 cups heavy cream
- 4-5 cloves garlic, minced
- 2 tbsp unsalted butter, melted
- 1 1/2 cups Gruyère cheese, shredded
- 1/2 cup Gouda (smoked or regular), shredded
- 1/2 cup Parmesan cheese, shredded
- 2 tbsp fresh thyme
- salt and pepper (to taste)
Instructions
- Preheat your oven to 375°F and grease a 9×13 baking dish.
- Peel the sweet potatoes. Using a mandoline or a sharp knife, slice them about 1/8 inch thick, as evenly as possible.
- In a saucepan, melt the butter over medium heat. Add the minced garlic and cook for a minute or two until fragrant. Add in the heavy cream and season with salt and pepper. Heat for a couple of minutes, just until it’s steaming with small bubbles around the edge, and don’t let it boil hard. (This mixture will not be super thick. But the sauce gets thicker as it cooks due to the potato starch.) Pour it into a measuring cup with a spout.
- Shred the Gruyère, Gouda, and Parmesan by hand and toss them together.
- Arrange a single layer of sweet potato slices in the baking dish, overlapping them slightly. Season with salt, pepper, and thyme.
- Pour a little of the cream mixture over the layer, just enough to lightly coat the slices, then sprinkle with some of the cheese. Repeat the layers. I usually do 3-4 layers. Make sure not to add too much cream to each layer.
- Sprinkle the remaining cheese mixture over the top of the dish.
- Cover the baking dish tightly with aluminum foil, crimping it around the rim, and bake for about 45 minutes.
- Remove the foil and bake for an additional 15-20 minutes, or until a knife slides easily into the center and the top is golden brown and bubbling.
- Let it rest for 10 minutes before serving.
Notes
- Skin on or off: You can leave the skin on if you’d rather skip peeling. Scrub the sweet potatoes well first, and expect the layers to be a little chewier.
- Layering: Don’t pack the layers too tightly.
- Browning: If the top browns too quickly, loosely tent the dish with foil.
- Pan size: A deep 9×9 works too and needs a few extra minutes in the oven, while a wider dish may finish a little faster. It’s done when the potatoes are fully tender and the center is bubbling.
- Make ahead: Assemble it up to 48 hours ahead, cover, and refrigerate. Take it out of the fridge 30 minutes before baking, then bake as directed, adding 10 to 15 minutes to the covered baking time.
- Storage: Store leftovers in an airtight container in the fridge for 3-4 days. Reheat individual portions in the microwave, or warm the full dish at 350°F for about 20 minutes.
- Dried thyme: Use 2 teaspoons of dried thyme in place of the fresh.
- Dairy-free: For a dairy-free or vegan version, try a thick, unsweetened dairy-free cream (like Silk), vegan butter, and dairy-free cheese shreds or nutritional yeast. Dairy-free shreds don’t melt as smoothly, so expect a looser, less gooey top.
Nutrition
Nutrition information is automatically calculated, so should only be used as an approximation.
I made this over the weekend for a dinner party and it was AMAZING!!! So So good. I highly recommend. The only thing is the heavy cream isn’t listed on the steps. I realized this in the process so I just added it to the pan with the butter & garlic, brought it to a boil and took it off of the burner. It wasn’t thick but it still baked up great.
Thank you Wendy! You added the cream at the right time. I’m so glad it was a hit. Thanks for trying!
This was AMAZING ! So easy and delicious. I swear I heard angels singing when I tasted it !
I’m so happy you enjoyed it. Happy Thanksgiving!
Delicious! We got a bunch of sweet potatoes from the farmer’s market, so we needed a way to use a LOT of sweet potato, and this perfect. We didn’t modify it in any way. Cutting the sweet potatoes with a mandoline was a bit difficult (I think our blade is not sharp enough), but the recipe is so good that we’ll keep it anyway. 🙂