# 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:
01 - Preheat oven to 375°F. Grease a 9x13-inch baking dish with butter or cooking spray.
02 - Melt 2 tablespoons butter in a medium saucepan over medium heat. Add 2 tablespoons all-purpose flour and whisk continuously for 1 minute to create a roux.
03 - Slowly pour 2 cups whole milk into the roux while whisking constantly to prevent lumps. Continue cooking for 3 to 4 minutes until the sauce thickens slightly.
04 - Remove saucepan from heat. Stir in 1 teaspoon salt, 1/2 teaspoon black pepper, 1/2 teaspoon garlic powder, and half of the shredded cheddar and mozzarella cheeses. Whisk until melted and smooth.
05 - Arrange half the sliced potatoes in the prepared baking dish. Top with half the onion slices, then pour half the cheese sauce over the layer. Repeat with remaining potatoes, onions, and cheese sauce.
06 - Sprinkle remaining shredded cheddar and mozzarella cheeses over the top. Dust with 1/4 teaspoon paprika.
07 - Cover the baking dish with aluminum foil and bake for 40 minutes at 375°F.
08 - Remove foil and bake an additional 25 to 30 minutes until potatoes are tender and the top is golden brown.
09 - Remove from oven and let rest for 10 minutes before serving to allow flavors to settle.