Ingredients:

  • 2 lbs (907g) Yukon Gold potatoes, peeled and thinly sliced
  • 1 medium (110g) yellow onion, thinly sliced
  • 2 tbsp (28g) unsalted butter, melted
  • 3 tbsp (42g) unsalted butter
  • 3 tbsp (24g) all-purpose flour
  • 2 cups (480ml) whole milk
  • 1 cup (240ml) heavy cream
  • 1 tsp (5g) garlic powder
  • 1 tsp (5g) salt
  • 1/2 tsp (2g) black pepper
  • 1/4 tsp (1g) ground nutmeg
  • 2 cups (225g) sharp cheddar cheese, shredded
  • 1/2 cup (50g) grated Parmesan cheese
  • 1 tsp (2g) smoked paprika

Instructions:

  1. Peel the potatoes and slice them into rounds approximately 1/8 inch (3mm) thick. Slice the onions into thin half-moons.
  2. Thoroughly grease a 9x13 inch baking dish with the 2 tbsp of melted butter to prevent sticking.
  3. Melt 3 tbsp of butter in a saucepan over medium heat. Whisk in the flour and cook for 1-2 minutes until nutty in aroma but not browned.
  4. Slowly pour in the milk and heavy cream, whisking constantly to eliminate lumps. Stir in the garlic powder, salt, pepper, and nutmeg.
  5. Simmer the sauce for 5 minutes until it thickens enough to coat the back of a spoon.
  6. Place a layer of sliced onions at the bottom of the baking dish. Arrange half of the sliced potatoes in overlapping rows and pour half of the cream sauce evenly over them.
  7. Repeat the process with the remaining potatoes and the rest of the cream sauce.
  8. Cover the dish with foil and bake at 375°F (190°C) for 45 minutes.
  9. Remove the foil, sprinkle the shredded cheddar and Parmesan evenly over the top, and dust with smoked paprika.
  10. Bake uncovered for another 20-30 minutes until the topping is bubbling and deep mahogany gold.