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Au Gratin Potatoes Recipe

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4.4 from 7 reviews

This classic Au Gratin Potatoes recipe features thinly sliced russet potatoes baked in a rich, creamy sauce made with caramelized onions, garlic, fresh thyme, and a blend of Gruyère and Parmesan cheeses. Topped with chives, this cheesy and flavorful dish makes a perfect comforting side for any meal.

Ingredients

Potatoes

  • 2 ½ lbs. russet potatoes, sliced 1/8-inch thick

Sauce

  • 1 small yellow onion, finely diced
  • 3 tablespoons salted butter
  • 4 cloves fresh garlic, minced
  • 2 teaspoons fresh thyme leaves
  • 2 cups heavy cream
  • ½ cup milk
  • 2 cups shredded Gruyère cheese
  • ½ cup grated Parmesan cheese
  • ¼ teaspoon salt
  • ¼ teaspoon pepper

Garnish

  • Chives, chopped

Instructions

  1. Preheat Oven: Preheat your oven to 350°F (175°C). This can also be done later after caramelizing the onions if preferred.
  2. Prepare Cream Mix: In a medium measuring cup, combine the heavy cream and milk. Warm the mixture in the microwave for 1 minute to temper it, then set aside.
  3. Caramelize Onions: In a soup pot over medium heat, melt the butter and add the diced onions. Soften the onions by cooking and stirring frequently for 10 minutes. Lower the heat to medium-low and continue cooking for an additional 10-15 minutes until the onions begin to brown and caramelize slightly.
  4. Add Garlic and Thyme: Stir in the minced garlic and fresh thyme leaves, cooking for 2 minutes until fragrant. Remove the pot from heat and allow to cool for 1 minute.
  5. Combine Cream and Cheese: Gradually stir the warmed cream and milk mixture into the pot, then return the heat to medium-high and bring to a boil. Remove from heat and slowly add the shredded Gruyère and grated Parmesan cheeses, stirring continuously to melt the cheeses into the sauce. Season with salt and pepper.
  6. Slice Potatoes: Using a sharp knife or mandoline slicer, slice the russet potatoes into 1/8-inch thick slices for even cooking.
  7. Layer Potatoes and Sauce: Lightly grease a 2.5-quart baking dish or a 9 x 13-inch pan. Arrange one-third of the potato slices in an even layer at the bottom of the dish. Lightly sprinkle with salt. Pour one-third of the cheese sauce over the potatoes. Repeat layering two more times, finishing with sauce on top.
  8. Bake Covered: Cover the baking dish and bake in the preheated oven for 1 hour to allow the potatoes to soften and absorb the flavors.
  9. Bake Uncovered: Remove the cover and continue baking uncovered for an additional 30 minutes to develop a golden crust.
  10. Optional Broil: For a more browned top, broil on high (425°F) for 1-2 minutes, watching carefully to avoid burning.
  11. Rest and Serve: Remove from oven and let the dish rest for 5-10 minutes to thicken the sauce. Garnish with chopped chives before serving.

Notes

  • Using a mandoline slicer ensures evenly thin potato slices for consistent cooking.
  • Do not slice potatoes thicker than 1/8 inch to avoid undercooked layers.
  • Tempering the cream and milk mixture helps prevent curdling when added to the hot onions.
  • Broiling at the end is optional but adds a beautiful golden crust and enhances flavor.
  • Letting the dish rest after baking allows the sauce to thicken, making it easier to serve.

Find it online: https://cookedbysarah.com/au-gratin-potatoes-recipe/