Ingredients:

  • 3 lbs Russet potatoes, scrubbed and peeled
  • 1 tsp fine sea salt
  • 1/2 tsp freshly cracked black pepper
  • 4 tbsp unsalted butter
  • 1/4 cup all-purpose flour
  • 3 cups whole milk, room temperature
  • 2 cloves garlic, minced into a paste
  • 1 tsp fresh thyme leaves, chopped
  • 1/4 tsp ground nutmeg
  • 1.5 cups Gruyere cheese, freshly grated
  • 1 cup extra sharp white cheddar, freshly grated
  • 1/2 cup Parmigiano-Reggiano, finely grated

Instructions:

  1. Peel 3 lbs of Russets and slice them into 1/8 inch rounds. Note: Uniform thickness ensures they all finish cooking at the same time.
  2. Melt 4 tbsp butter in a saucepan over medium heat, then whisk in 1/4 cup flour for 2 minutes until it smells slightly nutty.
  3. Slowly pour in 3 cups room temperature milk while whisking constantly.
  4. Add 2 minced garlic cloves, 1 tsp thyme, 1 tsp salt, 1/2 tsp pepper, and 1/4 tsp nutmeg.
  5. Simmer the sauce for 5 minutes until it coats the back of a spoon.
  6. Remove from heat and stir in 1 cup Gruyere and 1/2 cup white cheddar until completely melted and silky.
  7. Grease your 9x13 pan and lay half the potatoes down, then pour half the sauce over them. Repeat with the remaining potatoes and sauce.
  8. Sprinkle the remaining 1/2 cup Gruyere, 1/2 cup cheddar, and 1/2 cup Parmigiano Reggiano over the top.
  9. Cover with foil and roast at 375°F for 30 minutes.
  10. Remove the foil and roast for another 35 minutes until the top is golden and the edges sizzle.