Ingredients:

  • 2 lbs (900g) Yukon Gold potatoes, peeled and thinly sliced
  • 4 tbsp (57g) unsalted butter
  • 1/4 cup (30g) all-purpose flour
  • 3 cups (710ml) whole milk
  • 1 tsp kosher salt
  • 1/2 tsp freshly ground black pepper
  • 1/4 tsp ground nutmeg
  • 2 cloves garlic, minced
  • 1/2 cup (118ml) heavy cream
  • 2 cups (200g) shredded Gruyère cheese
  • 1/4 cup (25g) grated Parmesan cheese

Instructions:

  1. Peel and thinly slice the potatoes using a mandoline or knife. Even thickness is key for even cooking.
  2. Melt butter in a saucepan, whisk in flour, and cook for 1 minute. Gradually whisk in milk until smooth. Bring to a simmer, then reduce heat and cook until thickened, stirring constantly.
  3. Stir in salt, pepper, nutmeg, and minced garlic. Remove from heat and stir in heavy cream.
  4. Arrange a layer of potato slices in the baking dish. Pour a portion of the cream sauce over the potatoes, then sprinkle with a layer of cheese. Repeat layers until all potatoes and sauce are used, finishing with a generous layer of cheese.
  5. Bake in a preheated oven at 375°F (190°C) for 45-55 minutes, or until the potatoes are tender and the cheese is golden brown and bubbly. A knife should easily pierce the potatoes.
  6. Let the au gratin potatoes rest for 10-15 minutes before serving. This allows the sauce to thicken slightly and prevents a sloppy mess.