Au Gratin Sweet Potatoes

We’ve all had regular au gratin potatoes or cheesy potatoes, but have you tried au gratin sweet potatoes? I’m a huge fan of sweet potatoes, but only when they’re made in savory form. I’ve never cared for the traditional Thanksgiving casserole with marshmallows on top. Add cheese and cream though, and I’m in!

It’s important to slice the potatoes evenly, so if you can use a mandolin slicer that is your best option. It’s something I don’t use often, but is really key for dishes like this. I used two cheeses in this recipe, but you can really use whatever you like. Gruyere is such a nice gooey melting cheese, and I love the sharp flavor of the white cheddar. The rest is simply onions and garlic, cream, and some spices.

It feeds a crowd, and can be prepared ahead of time. Perfect if you’re hosting a holiday! Smaller crowd? Just cut the recipe in half and use a square pan. I will say that I tested freezing and re-heating and they were not anywhere nearly as good after frozen like some other potato dishes. The sweet potatoes just don’t hold up as well.

The brown, bubbly crispy bits on top are my FAVORITE. I love the flavor of the slightly burnt cheese, so good!

Another variation if you’re unsure about full-on sweet potatoes, try a combo! Last year I made a similar recipe and used half russet potatoes and half sweet potatoes and just intertwined the layers. It was delicious!

Dreamy, cheesy Au Gratin Sweet Potatoes, and the perfect addition to your Thanksgiving or Holiday table. Enjoy!

Shop this post

Au Gratin Sweet Potatoes

Course Side Dish
Prep Time 15 minutes
Cook Time 1 hour 15 minutes
Total Time 1 hour 30 minutes
Servings 8
Author Laura Doerr


  • 1 yellow onion sliced
  • 1 tbsp olive oil
  • 1 tbsp unsalted butter
  • 2 cloves garlic minced
  • 4 lbs sweet potatoes (about 5 potatoes) peeled and sliced thin (1/8 – 1/16 of an inch)
  • cups heavy cream
  • cups grated Gruyere cheese
  • 1 cup grated white cheddar cheese
  • 1 tbsp fresh thyme (or 1 tsp dried flakes)
  • 1/8 tsp fresh grated nutmeg
  • 1 tsp kosher salt
  • Black pepper


  1. Preheat oven to 350 degrees, and spray a 9×13 baking dish with nonstick cooking spray.

  2. Add olive oil, butter, and sliced onions to a medium skillet over medium heat. Season with a bit of salt and pepper. Sauté for about 5 minutes. Stir in minced garlic. Sauté for another 2-3 minutes until onions are translucent.

  3. In a large bowl combine the sliced sweet potatoes, heavy cream, thyme, nutmeg, kosher salt, and black pepper. Stir in sautéed onions, 1 cup of the Gruyere cheese, and the white cheddar cheese.

  4. Pour mixture into prepared baking dish, and arrange evenly, press down lightly. Top with remaining 3/4 cup of Gruyere cheese. Bake for 1 hour and 15 minutes until bubbly and golden brown on top. Allow to rest for about 10 minutes before serving.

Recipe Notes

For best results use a mandolin slicer for your potatoes for an even thin slice on all pieces.

This recipe would be equally delicious with russet or red potatoes, or a combination of root vegetables (potatoes, carrots, parsnips).

Can be made ahead of time, and re-heated in a preheated 350 degree oven for 20-30 minutes or until warmed through and bubbly again.

This post may contain affiliate links which won’t change your price but will share some commission.

Leave a comment

Recipe Rating