Ingredients:

  • 2 pounds (900g) Yukon Gold potatoes, peeled and thinly sliced
  • 1 large yellow onion, thinly sliced
  • 3 tablespoons (45g) unsalted butter
  • 3 tablespoons (25g) all-purpose flour
  • 3 cups (720ml) whole milk
  • 1 teaspoon (5ml) salt
  • ½ teaspoon (2.5ml) black pepper
  • ⅛ teaspoon (a pinch) ground nutmeg (optional)
  • 1 cup (100g) shredded Gruyere cheese (or cheddar), divided

Instructions:

  1. Preheat oven to 375°F (190°C). Grease a 9x13 inch baking dish.
  2. Melt butter in a large saucepan over medium heat. Add onion and cook until softened, about 5-7 minutes.
  3. Whisk in flour and cook for 1 minute, stirring constantly. Gradually whisk in milk until smooth.
  4. Bring to a simmer, stirring constantly, until slightly thickened (about 3-5 minutes). Remove from heat and stir in salt, pepper, and nutmeg (if using).
  5. Arrange a layer of potato slices in the prepared baking dish, overlapping slightly. Top with a layer of onion, then drizzle with some of the white sauce. Sprinkle with ⅓ of the cheese.
  6. Repeat layers of potatoes, onion, sauce, and cheese two more times, ending with a layer of potatoes and the remaining sauce. Sprinkle with remaining cheese.
  7. Cover the baking dish with aluminum foil and bake for 30 minutes. Remove the foil and bake for another 20-30 minutes, or until the potatoes are tender and the top is golden brown and bubbly.
  8. Let stand for 10-15 minutes before serving. This scalloped potatoes recipe is best when rested.