Directions:

Preheat oven to 400 degrees F

Coat a 13x9-inch baking dish with nonstick cooking spray.

Layer potatoes in prepared dish. Top with cheeses.

Melt butter in medium saucepan over medium heat; stir in flour; cook 1 minute.

Stir in milk, mustard, salt and pepper; bring to a boil. Reduce heat and cook, stirring constantly, until mixture thickens.

Pour mixture over cheese. Cover with foil. Bake 30 minutes.

Remove foil and bake 15 to 20 minutes or until potatoes are tender and top is brown.