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+ servings
Layers of sweet potato with cream sauce in between that has been topped with fresh sage and thyme in a white baking dish.

Sweet Potato Au Gratin

Krista Stechman
Thinly sliced layers of sweet potato baked in a creamy, cheesy sauce until tender with a golden brown top. These are a little sweet, a little savory and full of herbs and aromatics. The perfect side dish for holiday dinners.
5 from 2 votes
Prep Time 15 minutes
Cook Time 55 minutes
Total Time 1 hour 10 minutes
Course sides
Cuisine american
Servings 9 people
Calories 307 kcal

Equipment

  • 1 10x7 casserole dish https://amzn.to/3eejqky
  • 1 mandolin slicer https://amzn.to/3enbz4o
  • 1 small pot or pitcher
  • 1 ladle
  • 1 whisk
  • 1 peeler https://amzn.to/3q47NiL
  • 1 sharp chef's knife

Ingredients
  

Cream Sauce

  • 2 cups heavy cream
  • 5 cloves garlic minced
  • 1 tablespoon fresh thyme chopped
  • 2 teaspoon kosher salt
  • ½ teaspoon fresh sage finely chopped
  • ¼ tsp black pepper
  • teaspoon ground nutmeg

Potatoes + Cheese

  • 2 lbs sweet potatoes weight is after sweet potatoes have been peeled and sliced
  • 3 oz romano cheese grated

Instructions
 

Make the Cream Sauce

  • Whisk all ingredients for cream sauce together in a pitcher or small pot. Set aside

Making Sweet Potato Au Gratin

  • Preheat the oven to 400°F then spray a 10x7 casserole dish with non-stick cooking spray. Ladle a small amount of cream sauce into the dish to lightly cover the bottom
  • Peel the sweet potatoes then slice them to ⅛ inch thick on the mandolin slicer
  • Layer the sweet potatoes in the bottom of the pan slightly overlapping each other. Stir the cream then ladle a small amount of cream sauce over the potatoes and sprinkle them lightly with Romano cheese
  • Begin the next layer of sweet potatoes placing them in the opposite direction of the first layer. Ladle them with cream then a light sprinkle of Romano
  • Continue this process until all potatoes and cream are used up. Press the potatoes down so that the cream covers the top of them
  • Sprinkle the remaining Romano over the top of the dish then bake for 40 minutes, uncovered
  • Place aluminum foil over the top of the dish then continue baking another 15 minutes
  • Remove the sweet potato au gratin from the oven and allow to cool for about 30 minutes to set. Serve warm or at room temperature

Notes

  • Make sure to press the sweet potatoes down under the cream mixture a couple times during the layering and at the end. You want the cream to slightly cover the top of the potatoes.
  • The cream sauce will taste salty. That's okay, the potatoes will soak that all up and it will not be salty after it's cooked.
  • For the best results, give the cream mixture a stir right before each addition. The garlic sinks to the bottom and this makes for more evenly distributed flavor.
  • You can make this Homemade Sweet Potato Au Gratin up to 3 days ahead of time.

Nutrition

Calories: 307kcalCarbohydrates: 23gProtein: 6gFat: 22gSaturated Fat: 14gPolyunsaturated Fat: 1gMonounsaturated Fat: 6gCholesterol: 70mgSodium: 700mgPotassium: 411mgFiber: 3gSugar: 6gVitamin A: 15154IUVitamin C: 5mgCalcium: 173mgIron: 1mg
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