# What You'll Need:
→ Potatoes
01 - 3 pounds Yukon Gold or Russet potatoes, peeled and thinly sliced (about 1/8 inch)
→ Cheese Sauce
02 - 4 tablespoons unsalted butter
03 - 1 medium yellow onion, finely chopped
04 - 3 cloves garlic, minced
05 - 4 tablespoons all-purpose flour
06 - 2 1/2 cups whole milk, warmed
07 - 1 cup heavy cream
08 - 2 teaspoons Dijon mustard
09 - 1 teaspoon salt
10 - 1/2 teaspoon black pepper
11 - 1/2 teaspoon smoked paprika
12 - 2 cups sharp cheddar cheese, shredded
13 - 1 cup Gruyère cheese, shredded
→ Topping
14 - 1/2 cup shredded cheddar cheese
15 - 1/2 cup shredded Gruyère cheese
16 - 2 tablespoons chopped fresh chives (optional)
# Cooking Steps:
01 - Preheat oven to 350°F. Grease a 9x13 inch baking dish with butter or nonstick spray.
02 - Arrange half of the sliced potatoes in an even layer in the prepared baking dish.
03 - Melt butter in a large saucepan over medium heat. Add chopped onion and cook for 4 to 5 minutes until softened. Add garlic and cook for 1 additional minute.
04 - Sprinkle flour into saucepan and stir constantly for 1 to 2 minutes until well combined.
05 - Gradually whisk in warm milk and heavy cream, stirring continuously until mixture thickens, about 3 to 4 minutes.
06 - Add Dijon mustard, salt, black pepper, and smoked paprika; stir to combine.
07 - Remove saucepan from heat and whisk in shredded cheddar and Gruyère cheeses until fully melted and smooth.
08 - Pour half of the cheese sauce over the first potato layer. Arrange remaining potatoes on top, then pour remaining cheese sauce evenly over them.
09 - Cover dish with foil and bake for 45 minutes at 350°F.
10 - Remove foil. Sprinkle remaining cheddar and Gruyère cheeses over the top and bake uncovered for an additional 25 to 30 minutes until potatoes are tender and top is golden and bubbly.
11 - Allow to rest for 15 minutes before serving. Garnish with fresh chopped chives if desired.
