Potatoes Au Gratin
- 1/4 cup (1/2 stick) butter or margarine
- 1/4 cup flour
- 1 tsp salt
- 1/2 tsp dry mustard
- 1/4 tsp pepper
- 2 1/2 cups milk
- 1 pkg (8 oz) shredded cheddar cheese
- 2 tbsp chopped onion
- 6 cups thinly sliced potatoes
Preheat oven to 350°F. Melt butter in medium sauce pan on medium heat. Blend in flour, salt, mustard and pepper. Gradually add milk, stirring until well blended; cook until thickened, stirring constantly. Add 1½ cups of cheese and the onion; cook until cheese is melted, stirring frequently. Layer potatoes and cheese sauce alternating in 2 qt casserole dish, ending with a layer of cheese sauce.
Bake for 1 hour 15 minutes or until potatoes are tender. Sprinkle with remaining cheese. Bake an additional 5 minutes or until cheese is melted.