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Classic Sweet Potato Au Gratin with Gruyère and Thyme

A close-up slice of creamy sweet potato au gratin with layers of orange sweet potato and white sauce, topped with browned cheese and herbs.
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Make this creamy, savory sweet potato au gratin for an elegant holiday side dish or a comforting weeknight meal.

Ingredients

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  • 3 lbs sweet potatoes, peeled and thinly sliced
  • 1 tablespoon unsalted butter, plus more for greasing
  • 2 cloves garlic, minced
  • 1/2 cup heavy cream
  • 1/2 cup whole milk
  • 1/4 teaspoon ground nutmeg
  • 1/2 teaspoon salt
  • 1/4 teaspoon black pepper
  • 1 cup Gruyère cheese, shredded
  • 1/2 cup Parmesan cheese, grated
  • 1 tablespoon fresh thyme leaves

Instructions

  1. Preheat your oven to 375 degrees F. Grease a 9×13 inch baking dish with butter.
  2. In a small saucepan over medium heat, melt the 1 tablespoon of butter. Add the minced garlic and cook for 1 minute until fragrant. Do not brown the garlic.
  3. Whisk the heavy cream, milk, nutmeg, salt, and pepper into the saucepan. Heat the mixture until it just begins to simmer, then remove from heat.
  4. In a large bowl, toss the thinly sliced sweet potatoes with half of the shredded Gruyère cheese, half of the Parmesan cheese, and the fresh thyme leaves.
  5. Arrange half of the sweet potato mixture in an even layer in the prepared baking dish. Pour half of the warm cream mixture evenly over the potatoes.
  6. Repeat the layering process with the remaining sweet potatoes, followed by the remaining cream mixture.
  7. Sprinkle the remaining Gruyère and Parmesan cheese evenly over the top layer.
  8. Bake for 50 to 60 minutes, or until the sweet potatoes are tender when pierced with a fork and the top is golden brown and bubbly. If the top browns too quickly, loosely cover the dish with foil for the last 15 minutes of baking.
  9. Let the sweet potato au gratin rest for 10 minutes before slicing and serving.

Notes

  • For a make-ahead option, assemble the entire gratin, cover it tightly, and refrigerate for up to 24 hours. Add 10 to 15 minutes to the baking time if baking directly from the refrigerator.
  • You can substitute Gruyère with sharp white cheddar for a different flavor profile.
  • If you want a richer flavor, replace 1/4 cup of the milk with dry white wine.

Nutrition

Find it online: https://cheffinity.com/sweet-potato-au-gratin-recipe/