# 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 tablespoons unsalted butter
07 - 2 tablespoons all-purpose flour
→ Seasonings
08 - 1 teaspoon salt
09 - 1/2 teaspoon black pepper
10 - 1/2 teaspoon garlic powder
11 - 1/4 teaspoon paprika
# How-To Steps:
01 - Preheat oven to 375°F. Grease a 9x13-inch baking dish with butter or non-stick spray.
02 - Melt butter in a medium saucepan over medium heat. Add flour and whisk continuously for 1 minute to form a smooth roux.
03 - Slowly pour 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, pepper, garlic powder, and half of the cheddar and mozzarella cheeses until completely melted and smooth.
05 - Arrange half of the sliced potatoes in the prepared baking dish. Top with half of the onion slices and half of the cheese sauce. Repeat with remaining potatoes, onions, and cheese sauce.
06 - Sprinkle the remaining shredded cheddar and mozzarella cheeses over the top. Dust with paprika.
07 - Cover the baking dish tightly with aluminum foil. Bake for 40 minutes.
08 - Remove foil and bake for an additional 25 to 30 minutes until potatoes are tender and the top is golden brown.
09 - Remove from oven and allow the dish to rest for 10 minutes before serving.
