Ingredients:

  • 2 lbs (900g) Yukon Gold potatoes, peeled and thinly sliced (about 1/8 inch thick)
  • 1 tbsp (15ml) olive oil
  • 1 tsp (5g) kosher salt
  • ½ tsp (2.5g) freshly ground black pepper
  • 4 tbsp (57g) unsalted butter
  • 4 tbsp (32g) all-purpose flour
  • 3 cups (710ml) whole milk, warmed
  • 2 cloves garlic, minced
  • 1 tsp fresh thyme leaves, chopped
  • ½ tsp (2.5g) kosher salt
  • ¼ tsp (1.25g) freshly ground white pepper
  • Pinch of ground nutmeg
  • 1 ½ cups (150g) Gruyère cheese, grated
  • ½ cup (50g) Parmesan cheese, grated

Instructions:

  1. Toss potato slices with olive oil, salt, and pepper. Set aside.
  2. Melt butter in saucepan. Whisk in flour; cook for 1-2 minutes (roux). Gradually whisk in warm milk until smooth. Bring to a simmer, stirring constantly.
  3. Stir in garlic, thyme, salt, white pepper, and nutmeg. Simmer for 5 minutes, stirring occasionally, until thickened.
  4. Layer potato slices in baking dish, overlapping slightly. Pour béchamel sauce evenly over the potatoes, ensuring all are coated.
  5. Sprinkle Gruyère and Parmesan cheeses evenly over the sauce.
  6. Bake in preheated oven at 375°F (190°C) for 1 hour 15 minutes, or until potatoes are tender and the cheese is golden brown and bubbly. Check for doneness by piercing with a fork.
  7. Let stand for 10 minutes before serving.