Preheat your oven to 375°F (190°C).

Melt 2 tablespoons of butter in a medium saucepan over medium heat, and stir in ½ cup of flour to create a roux.

Gradually whisk in 2 cups of milk, stirring until thickened, about 3-5 minutes. Add salt, pepper, 1 cup of sharp cheddar, and 1 cup of Gruyère cheese, mixing until smooth.

Layer half of the sliced Yukon Gold potatoes in a greased 9x13 baking dish and pour half of the cheese sauce over them.

Repeat with remaining potatoes and cheese sauce.

Sprinkle 1 cup of breadcrumbs over the top layer.

Cover with foil and bake for 45 minutes. Uncover and bake for an additional 15-20 minutes until golden.

Let it rest for 10 minutes before serving. Garnish with freshly chopped chives.