# What You'll Need:
→ Vegetables
01 - 2 lbs Yukon Gold or Russet potatoes, peeled and thinly sliced
02 - 1 medium yellow onion, thinly sliced
→ Dairy
03 - 2 cups shredded sharp cheddar cheese
04 - 1 cup shredded mozzarella cheese
05 - 2 cups whole milk
06 - 2 tbsp unsalted butter
07 - 2 tbsp all-purpose flour
→ Seasonings
08 - 1 tsp salt
09 - ½ tsp black pepper
10 - ½ tsp garlic powder
11 - ¼ tsp paprika
# Steps to Follow:
01 - Preheat oven to 375°F. Grease a 9x13-inch baking dish with butter or cooking spray.
02 - Melt 2 tbsp butter in a medium saucepan over medium heat. Add 2 tbsp flour and whisk continuously for 1 minute to form a roux.
03 - Slowly pour 2 cups milk into the roux while whisking constantly to prevent lumps. Continue cooking until the mixture thickens slightly, approximately 3 to 4 minutes.
04 - Remove from heat. Stir in salt, black pepper, garlic powder, and half of the shredded cheddar and mozzarella cheeses until completely melted and smooth.
05 - Arrange half the potato slices in the prepared baking dish. Top with half the onion slices, then half the cheese sauce. Repeat with remaining potatoes, onions, and cheese sauce.
06 - Sprinkle the reserved shredded cheeses and paprika evenly over the top layer.
07 - Cover the baking dish with aluminum foil and bake for 40 minutes at 375°F.
08 - Remove foil and bake for an additional 25 to 30 minutes, or until potatoes are tender and the top is golden brown.
09 - Allow the dish to rest for 10 minutes before serving to set the layers and ensure even portions.