Potatoes au Gratin

In this rich, beautiful gratin, potatoes and onions are arranged in concentric circles, coated in a creamy cheese sauce, and topped off with a few more handfuls of shredded cheese. Cheddar and Gruyère work wonderfully here, but feel free to substitute with another one of your favorite melting cheeses, such as Fontina or Havarti. A quick run under the broiler at the end browns the top of the gratin for a little extra flavor and texture.

Potatoes au Gratin
Photo: Photo by Greg DuPree / Food Styling by Chelsea Zimmer / Prop Styling by Kay Clarke
Active Time:
35 mins
Total Time:
2 hrs
Servings:
8

Ingredients

  • 1 medium garlic clove, halved

  • 3 tablespoons unsalted butter, at room temperature

  • 3 pounds medium-size red potatoes, unpeeled and cut into 1/8-inch-thick slices

  • 1 medium-size (9 ounce) yellow onion, thinly sliced (about 2 cups)

  • 1 tablespoon all-purpose flour

  • 1 ¾ cups heavy whipping cream

  • 2 ½ teaspoons kosher salt

  • 1 teaspoon dry mustard

  • teaspoon freshly grated nutmeg

  • 6 ounces sharp white cheddar cheese, shredded (about 1 1/2 cups), divided

  • 4 ounces Gruyère cheese, shredded (about 1 cup), divided

  • 2 teaspoons thinly sliced fresh chives

Directions

  1. Preheat oven to 325°F. Rub cut sides of garlic all over inside of a 2 1/2- to 3-quart oval broiler-safe baking dish; discard garlic. Rub inside of dish with 1 tablespoon butter; set aside.

  2. Arrange potato and onion slices, standing slightly vertically on edges, in slightly overlapping concentric circles in the baking dish. Tuck smaller potato and onion slices into any gaps in dish to fill. Cover with a damp paper towel until ready to use.

  3. Heat remaining 2 tablespoons butter in a medium saucepan over medium until melted and foaming. Add flour; cook, whisking constantly, for 1 minute. Slowly whisk in cream until smooth. Whisk in salt, mustard, and nutmeg. Bring to a simmer over medium, whisking constantly. Remove from heat. Whisk in 3/4 cup of the Cheddar and 1/2 cup of the Gruyère, 1 handful at a time, until melted and smooth. Pour evenly over potato mixture. Sprinkle with remaining 3/4 cup Cheddar and 1/2 cup Gruyère.

  4. Cover baking dish with aluminum foil. Bake in preheated oven until cream is bubbling, cheese has melted, and potatoes are tender when pierced with a fork, 1 hour to 1 hour, 15 minutes. Carefully remove foil from baking dish, while keeping dish in oven. Increase oven temperature to broil. Broil gratin until cheese is bubbly and browned in spots, checking occasionally to prevent over-browning, 5 to 8 minutes. Remove from oven. Let stand 20 minutes. Sprinkle with chives and serve.

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