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

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!!

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

★★★★★ 4.9 from 7 reviews
  • Author: Laura Bolton – Fork Knife Swoon
  • Prep Time: 20 mins
  • Cook Time: 50 mins
  • Total Time: 1 hour 10 minutes
  • Yield: 4–6 Servings 1x
  • Category: Side Dish, Savory, Dinner, Holiday
  • Method: Baking
  • Cuisine: American, French
  • Diet: Vegetarian
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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
  • 1–1/2 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!!

Equipment

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 added November 2018.