Au Gratin Potatoes

3 tablespoons butter
3 tablespoons flour
1 1/2 teaspoons salt
1/8 teaspoon pepper
2 cups 2% milk
1 cup shredded cheddar cheese
1/2 cup shredded Gruyere cheese
5 cups thinly sliced peeled potatoes (about 6 medium)
1/2 cup finely chopped onion

Preheat oven to 400 degrees.

Layer potatoes and onions in a greased casserole dish.

Melt butter in a sauce pan and whisk in flour. Cook 2-3 minutes. Add seasonings and milk. Whisk over medium heat until thick and bubbly. Remove from heat and stir in cheeses until melted.

Pour cheese sauce over potatoes and cover with foil (sprayed with cooking spray) and bake for 1 hour. Remove foil and bake an additional 20 minutes or until lightly browned.

**You can cut down cooking time to 45 minutes by microwaving potatoes and onions in the casserole dish for 10 minutes before adding the cheese sauce.