Ingredients:

  • 4 pounds Russet or Yukon Gold Potatoes, peeled and uniformly sliced 1/8 inch thick (do not rinse)
  • 3 Tbsp unsalted butter
  • 3 Tbsp all-purpose flour
  • 2 cups heavy cream
  • 1 cup whole milk
  • 12 ounces Gruyère Cheese, grated and divided (2/3 for sauce, 1/3 for topping)
  • 2 cloves fresh garlic, minced
  • 1/4 tsp ground nutmeg
  • Salt and freshly ground black pepper (to taste)

Instructions:

  1. Preheat your oven to 375°F (190°C). Generously grease a 9x13 inch baking dish with butter. In a saucepan, melt the 3 Tbsp butter. Whisk in the flour and cook for one minute to form a roux until it smells nutty.
  2. Gradually whisk in the warm 1 cup whole milk and 2 cups heavy cream until the sauce starts to gently simmer and thicken slightly. Remove from heat.
  3. Stir in the minced garlic, salt, pepper, and 1/4 tsp of nutmeg. Stir in 2/3 of the grated Gruyère until it melts completely into a velvety smooth sauce. Taste and adjust seasoning, noting it should be slightly salty at this stage.
  4. Spread a thin layer of the cream sauce across the bottom of the greased dish. Arrange one-third of the potato slices, overlapping them slightly. Pour one-third of the remaining sauce evenly over the top. Repeat two more times, ending with a final generous layer of sauce (using all the sauce).
  5. Tightly cover the dish with foil. Bake at 375°F for 45 minutes. This traps steam and ensures the potatoes soften completely.
  6. Remove the foil. Sprinkle the remaining 1/3 of the Gruyère evenly over the top. Return the dish to the oven and bake for an additional 45 minutes, or until the surface is deep golden brown, bubbling, and a sharp knife slides easily through the center layer of potatoes.
  7. Let the potatoes au gratin rest for 15 minutes before slicing and serving. This allows the sauce to set properly and prevents it from running.