Ingredients:

  • 3 lbs Russet potatoes, peeled and sliced into 1/8-inch rounds
  • 1 large yellow onion, thinly sliced into half-moons
  • 4 tbsp unsalted butter
  • 1/4 cup all-purpose flour
  • 2.5 cups whole milk, room temperature
  • 1 cup heavy cream
  • 2 tsp kosher salt
  • 1 tsp freshly cracked black pepper
  • 1/2 tsp garlic powder
  • 2 cups sharp yellow cheddar cheese, freshly shredded
  • 8 slices thick-cut bacon, cooked until crispy and chopped
  • 1/2 cup full-fat sour cream
  • 1/4 cup fresh chives, finely minced
  • 1/2 cup Monterey Jack cheese, shredded

Instructions:

  1. Preheat your oven to 375°F (190°C) and generously grease a 9x13 inch ceramic baking dish with butter.
  2. Peel and slice the Russet potatoes into 1/8-inch uniform rounds using a mandoline. Submerge them in cold water to prevent oxidation, then pat thoroughly dry with a kitchen towel.
  3. In a large heavy-bottomed saucepan, melt the butter over medium heat. Add the sliced onions and sauté until translucent and soft.
  4. Whisk in the flour and cook for 2 minutes to create a blond roux, ensuring the raw flour taste is cooked out.
  5. Slowly stream in the milk and heavy cream, whisking constantly to prevent lumps. Simmer until the sauce thickens enough to coat the back of a spoon.
  6. Remove the sauce from heat. Stir in the kosher salt, black pepper, garlic powder, sour cream, and 1.5 cups of the shredded sharp cheddar until the cheese is completely melted and the sauce is smooth.
  7. Arrange 1/3 of the dried potato slices in the prepared baking dish. Pour 1/3 of the cheese sauce over the potatoes and sprinkle with some of the crispy chopped bacon.
  8. Layer another 1/3 of the potatoes on top, followed by another 1/3 of the cheese sauce, 1/2 cup of the sharp cheddar, and some chopped bacon.
  9. Repeat with the final 1/3 of potatoes, sauce, and cheddar, and bacon.
  10. Top the casserole with the Monterey Jack cheese and the remaining bacon.
  11. Cover the dish with foil and bake for 45 minutes. Remove the foil and bake for an additional 25-30 minutes until the potatoes are tender and the top is bubbly and golden brown.
  12. Garnish with fresh minced chives and let the casserole rest for 10 minutes before serving to allow the sauce to set.