Ingredients:

  • 3 lbs Russet or Yukon Gold Potatoes, peeled and uniformly sliced (1/8 inch thick)
  • 4 Tbsp Unsalted Butter
  • 4 Tbsp All-Purpose Flour
  • 3 cups Whole Milk, warmed
  • 1 cup Heavy Cream (or Double Cream)
  • 6 oz Gruyère Cheese, grated (divided)
  • 4 oz Sharp Cheddar Cheese, grated (divided)
  • 1/4 tsp Freshly Grated Nutmeg
  • 1 clove Garlic, finely minced (for rubbing dish)
  • 5 tsp Kosher or Sea Salt (to taste)
  • Freshly Ground Black Pepper (to taste)

Instructions:

  1. Preheat oven to 375°F (190°C). Rub the inside of a 9x13 inch baking dish generously with the cut side of the garlic clove.
  2. Melt butter in a large saucepan over medium heat. Whisk in the flour and cook for 1–2 minutes to form a blonde roux.
  3. Gradually whisk in the warm milk until smooth. Bring to a gentle simmer, whisking constantly, until the sauce thickens enough to coat the back of a spoon (about 5–7 minutes). Remove from heat.
  4. Stir the heavy cream, nutmeg, half of the Gruyère, and half of the Cheddar into the thickened sauce. Season well with salt and pepper to create the Mornay sauce.
  5. Arrange one-third of the thinly sliced potatoes evenly in the prepared baking dish. Sprinkle lightly with salt and pepper.
  6. Pour one-third of the cheese sauce evenly over the first layer of potatoes.
  7. Repeat the layering process twice more: Potatoes, seasoning, sauce.
  8. Sprinkle the remaining grated Gruyère and Cheddar cheese evenly over the top layer.
  9. Cover the dish tightly with foil and bake for 35 minutes.
  10. Remove the foil and continue baking for another 20–30 minutes, or until the top is deeply golden brown and the potatoes are completely tender.
  11. Let the Cheesy Au Gratin Potatoes rest for 10–15 minutes before slicing and serving to allow the sauce to set.