Ingredients:

  • 3 lbs Yukon Gold potatoes, sliced into 1/8-inch rounds
  • 1 yellow onion, thinly sliced into half-moons
  • 3 cloves garlic, minced
  • 4 tbsp unsalted butter
  • 1/4 cup all-purpose flour
  • 3 cups whole milk
  • 1 cup heavy cream
  • 1 tsp salt
  • 1/2 tsp black pepper
  • 1/4 tsp ground nutmeg
  • 1 tbsp fresh thyme, finely chopped

Instructions:

  1. Preheat your oven to 350°F (180°C). Grease a 9x13-inch baking dish with butter or non-stick spray.
  2. Wash and peel the Yukon Gold potatoes. Use a mandoline slicer to create uniform 1/8-inch thick rounds.
  3. In a large saucepan over medium heat, melt 4 tablespoons of unsalted butter. Whisk in 1/4 cup of all-purpose flour and cook for 1-2 minutes to create a blonde roux.
  4. Slowly whisk in the whole milk and heavy cream, ensuring no lumps remain. Simmer until the sauce thickens enough to coat the back of a spoon.
  5. Stir in the minced garlic, salt, black pepper, nutmeg, and fresh thyme. Remove from heat.
  6. Layer half of the sliced potatoes and onions into the prepared baking dish. Pour half of the cream sauce over the layer. Repeat with the remaining potatoes, onions, and sauce.
  7. Cover the dish tightly with aluminum foil. Bake for 45 minutes to trap steam and hydrate the potato starch.
  8. Remove the foil and bake for an additional 30 minutes until the top is bubbling and has developed a deep mahogany-colored crust.
  9. Let the dish rest for 10 minutes before serving to allow the sauce to set into a velvety consistency.