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–+ servings
A baking dish filled with roasted potatoes and a wooden spoon.

Sweet Potato Au Gratin recipe

These au gratin sweet potatoes are cheesy, creamy, and a delicious spin on your regular potato au gratin. It's the perfect addition to any holiday table!
Prep 30 minutes
Cook 1 hour
Total 1 hour 30 minutes
Fat 16
Carbs 24
Protein 10
Yield 10

Ingredients

  • 3 large sweet potatoes any color

Au Gratin Sauce

  • 6 tablespoons unsalted butter
  • ½ medium yellow onion minced
  • ½ teaspoon sea salt separated
  • 6 cloves garlic minced
  • ⅓ cup all-purpose flour
  • ½ teaspoon cracked black pepper
  • 1 tablespoon chopped fresh thyme
  • 1.5 cups 2% milk
  • 1 cup chicken broth
  • 1 cup grated parmesan cheese
  • 1 cup shredded gruyere cheese

Topping

  • 15 Ritz crackers crumbled
  • 2 tablespoons fresh thyme

Instructions

  • Preheat the oven to 400ºF and grease a 9x13-inch casserole dish.
  • Prepare the sweet potatoes by using a mandolin to slice them into uniform rounds. A 1.3mm or 2mm thickness works for this recipe. Try to avoid thicker potato slices. Set the potatoes aside.
    A bowl full of sweet potato slices.
  • Prepare the au gratin sauce. Melt butter in a large skillet over medium/high heat. When the butter is melted, add the onion and ¼ teaspoon of salt. Saute for 3-4 minutes. Add the garlic and saute until fragrant, about 1 minute.
    A frying pan with a wooden spoon in it.
  • Add the flour, pepper, and fresh thyme to the skillet and mix with the ingredients until it turns into a paste. Cook the mixture for at least 1 minute.
  • Turn the heat to medium heat and slowly add the milk to the skillet, whisking constantly so the milk doesn’t burn. Once all the milk has been added, it should thicken quickly.
  • Slowly add the broth to the skillet, whisking to combine and thicken.
  • Remove the mixture from the heat and add the parmesan and gruyere cheese a little bit at a time, whisking vigorously until melted. The mixture should be smooth (except for the onion and garlic) and thick.
  • Add 1 cup of cheese sauce to the bottom of the 9x13-inch dish. Spread it out evenly. Place the sweet potato rounds, skin side up, into the dish. The sweet potatoes should fill the entire dish.
    Sliced sweet potatoes in a baking dish.
  • Pour the remaining sauce evenly over the potatoes. Use a spatula to push the sauce down and in between the potatoes.
  • Lastly, spread the Ritz cracker crumbs over the top of the potatoes and cover the casserole dish.
    A baking dish filled with fruit and nuts.
  • Bake for 30 minutes covered and 30 minutes uncovered.
  • Remove from the oven and let the potatoes rest for 10 minutes before serving. Top with the remaining fresh thyme.
    Sweet potato casserole in a baking dish with a wooden spoon.

Tips & Notes

  • Gluten-free bread crumbs can be used in place of the Ritz crackers.
  • The dish must be uncovered for the second half of the bake time so the sauce can cook off and thicken.

Watch it

Nutrition Facts

Calories: 279kcal | Carbohydrates: 24g | Protein: 10g | Fat: 16g | Fiber: 3g | Sugar: 5g