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The Best Make-Ahead Gruyère Thyme Potato Gratin

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This make-ahead Gruyère thyme potato gratin is rich, creamy, and packed with flavor. Assemble it a day ahead, pop it in the fridge, and bake when your guests are on their way—the flavors get even better overnight.

Ingredients

Scale
  • 3 pounds Yukon Gold potatoes (about 6–7 medium potatoes, peeled and sliced ⅛-inch thick)
  • 2 cups heavy cream (480 ml)
  • 1 cup whole milk (240 ml)
  • 2 cups grated Gruyère cheese (about 8 ounces)
  • 1 cup grated Parmesan cheese (about 4 ounces)
  • 4 cloves garlic (minced)
  • 2 tablespoons fresh thyme leaves (or 2 teaspoons dried)
  • 1 teaspoon kosher salt
  • ½ teaspoon freshly ground black pepper
  • 2 tablespoons unsalted butter (for greasing the dish)
  • ½ cup caramelized onions (optional)
  • ¼ teaspoon freshly grated nutmeg (optional)
  • 1 cup cooked, crumbled bacon (optional)

Instructions

  1. Peel the potatoes and slice them into ⅛-inch thick rounds using a mandoline or a sharp knife. Place the sliced potatoes in a large mixing bowl.
  2. In a separate bowl or large measuring cup, whisk together the heavy cream, whole milk, minced garlic, thyme leaves, salt, and pepper. Pour this mixture over the potato slices and toss gently until every slice is coated.
  3. Grease a 9×13-inch baking dish with the butter. Start layering the potato slices in the dish, overlapping them slightly like shingles. After every two layers, sprinkle a handful of the grated Gruyère and Parmesan cheese. Repeat for about 4-5 layers total. Pour any remaining cream mixture over the top.
  4. Sprinkle the remaining Gruyère and Parmesan evenly over the top layer. If using caramelized onions or bacon, scatter them between the layers now.
  5. Cover the dish tightly with aluminum foil and refrigerate for up to 24 hours.
  6. When ready to bake, preheat the oven to 375°F (190°C). Remove the dish from the fridge and let it sit on the counter for about 20 minutes. Bake covered with foil for 45 minutes. Then remove the foil and bake for another 15-30 minutes, until the top is golden brown and bubbly, and a knife inserted into the center slides through the potatoes with no resistance.
  7. Let the gratin rest for at least 10 minutes before serving.

Notes

Don’t skip the resting step after baking—it allows the cream to set for clean slices. Use a mandoline for even slices. Grate your own cheese for best melting. Season between layers for even flavor. If the top browns too quickly, tent with foil.

Nutrition

Keywords: potato gratin, make-ahead, Gruyère, thyme, holiday side dish, creamy potato casserole

Find it online: https://goldensimmer.com/the-best-make-ahead-gruy-e-re-thyme-potato-gratin/