# Required Ingredients:
→ 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)
# Preparation Steps:
01 - Preheat oven to 350°F. Grease a 9x13-inch baking dish with butter or nonstick spray.
02 - Place half of the sliced potatoes evenly in the prepared baking dish.
03 - Melt butter in a large saucepan over medium heat. Sauté chopped onion for 4 to 5 minutes until softened, add garlic and cook for an additional minute.
04 - Stir in flour and cook constantly for 1 to 2 minutes to form a roux.
05 - Gradually whisk in warmed milk and cream, stirring continuously until mixture is smooth and thickened, about 3 to 4 minutes.
06 - Add Dijon mustard, salt, black pepper, and smoked paprika. Remove from heat and whisk in shredded cheddar and Gruyère until fully melted and smooth.
07 - Pour half the cheese sauce over the potato layer. Add remaining potatoes, then top with remaining sauce, spreading evenly.
08 - Cover with foil and bake for 45 minutes.
09 - Remove foil, sprinkle remaining cheddar and Gruyère cheeses on top, and bake uncovered for 25 to 30 minutes until potatoes are tender and the surface is golden and bubbly.
10 - Let the dish rest for 15 minutes before serving. Garnish with fresh chives if desired.
