Extra Cheesy Sweet Potato Gratin: The Perfect Side Dish

Most Popular, Perfect Side Dishes

Listen, it’s a miracle I pulled myself from a pan of this cheesy sweet potato gratin long enough to actually post it to the world wide web. Here you are web! Your next perfect side dish for any meal.

A gratin is anything that is baked until golden brown either with breadcrumbs or cheese. Mine has cheese. Just all the cheese. No room for breadcrumbs. Cheese-room-only.

For Thanksgiving I brought my savory mashed sweet potatoes to our gathering. During dinner, two fellas stood up and thanked, “whoever brought the mashed sweet potatoes.” Everyone, this is the ultimate encouragement for me! And it also made me want to explore another sweet potato side dish.

This one has cheese. Have we mentioned cheese? I use two different kinds, gruyere and parmesan. Gruyere has a milder Swiss cheese flavor. I don’t love Swiss cheese but I love the decadent flavor of gruyere – it feels like a treat. And it melts very well. But if you want another cheese, go for Fontina which is also very melty but on the milder side.

Extra Cheesy Sweet Potato Gratin: The Perfect Side Dish

We’re just going to slice the sweet potatoes extra thin. Like 1/8 of an inch.

You can do this with a very sharp knife or a mandoline. Speaking of a mandoline, I now own one! I used to do all my thin slicing with my sharp knife but a mandolin cuts down on the time.

I researched A LOT. And I have this mandoline.

I actually checked on the return policy because I was 100% sure I would not be amused and return it. I am happy to report I am a verified believer. I’m so happy this is now in my kitchen. It’s also perfect for slicing butternut squash for my butternut squash lasagna or for cutting sweet potato fries in a flash.

This dish is one big layer of sweet potatoes, sautéed onions and herbs, cream and butter, and of course cheese.

Bonus? I assemble this up to two days ahead of time, seal it with an airtight lid and place it in the refrigerator. Then I can pop it into the oven on the day I want to make it.

Pro tip: get one of the corner pieces, where the potatoes are surrounded by extra crispy cheese.


Extra Cheesy Sweet Potato Gratin: The Perfect Side Dish

This cheesy sweet potato gratin is the perfect side dish for any meal or gathering! The cheese and cream make it extra savory and decadent while the sweet potatoes add a hint of sweetness.

  • Author: Bri McKoy


  • 2 lbs sweet potatoes, peeled and thinly sliced (about 1/8 inch thickness)
  • 2 TBS butter, divided
  • 1 TBS olive oil
  • 1 yellow onion, chopped
  • 1/2 TBS fresh thyme
  • 1 tsp rosemary
  • 1 tsp salt
  • 1/4 tsp pepper
  • 1 cup heavy cream
  • 1 cup (5 ounces or .30 lbs) gruyere or fontina cheese, shredded
  • 1 cup parmesan cheese, shredded and divided


  1. Preheat oven to 400 degrees.
  2. Peel and then thinly slice sweet potatoes. To get an even thin slice use a mandoline or slice with a sharp knife. Should be about 1/8 inch thick.
  3. In a sauce pan add 1 TBS butter and olive oil. Once the butter is melted add the onion, thyme, rosemary, salt and pepper. Saute until the onion is soft, about 3-5 minutes. Set aside.
  4. In a sauce pot, add the heavy cream and 1 TBS of butter. Bring to a simmer on medium high heat. Once bubbling, remove from burner and set aside.
  5. In a baking dish, add a layer of the sweet potatoes (it is ok if the potatoes slightly overlap each other). Then add the onion mixture. Then add some of the gruyere and parmesan cheese (only use 1/2 cup of the parmesan for the layering, reserve the other 1/2 cup for the top layer). Repeat with another layer of sweet potatoes, onion mixture and cheese until all ingredients are used. The last item should be the onion mixture (do not add a top layer of cheese).
  6. Slowly pour the heavy cream sauce over the whole dish of sweet potatoes.
  7. Bake for 40 minutes.
  8. After 40 minutes, remove the baking dish from the oven. Set the oven to broil. Sprinkle the remaining 1/2 cup parmesan cheese on top of the sweet potatoes and return to oven. Bake until cheese is melty and bubbly – about 5-10 more minutes.
  9. Allow to sit for 10-20 minutes so the juices will settle and thicken. Serve!


Can be assembled up to two days ahead of time. Place an airtight lid over dish and refrigerator until ready to bake.

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  1. Heather Roy says:

    Wondering if you have the nutritional information for this dish?

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