Preheat your oven to 375°F (190°C).

Melt 2 tablespoons of butter in a medium saucepan over medium heat. Whisk in ½ cup of all-purpose flour for about 2-3 minutes until smooth.

Gradually add 2 cups of milk to the roux while whisking constantly until thickens and bubbles for 5-7 minutes. Remove from heat and fold in the cheeses until melted.

In a greased baking dish, layer half of the sliced Yukon Gold potatoes and pour half of the cheese sauce over them.

Repeat the layers with the remaining sliced potatoes and cheese sauce.

Sprinkle 1 cup of breadcrumbs evenly over the top layer of cheese sauce.

Cover with aluminum foil and bake for 45 minutes.

Remove the foil and bake for an additional 15-20 minutes until golden brown and bubbly.

Let the dish rest for 10 minutes before serving.