Potatoes Au Gratin

Ingredients

Instructions

1. 1preheat oven
2. 2Preheat oven to 400°F.
3. 3prep potatoes
4. 4Wash potatoes and slice into ⅛" thin slices. Slice onion as thin as possible.
5. 5assemble
6. 6Season the potatoes and onions with ½ teaspoon of salt and ¼ teaspoon of pepper. Toss well to evenly coat. Layer potatoes and onions into little stacks. Place stacks on their side in a greased 2.5qt to 3qt casserole dish.
7. 7make sauce
8. 8Melt butter and flour in a saucepan and cook 2 to 3 minutes. Add mustard powder, ¼ teaspoon salt, ¼ teaspoon pepper and milk. Whisk over medium heat until thick and bubbly. Remove from heat and stir in cheeses until melted.
9. 9bake
10. 10Pour the cheese sauce over the potatoes, gently separating them to allow the sauce to seep between the layers. Cover with foil (sprayed with cooking spray) and bake 60 minutes.
11. 11brown
12. 12Remove foil and bake an additional 20 to 30 minutes or until lightly browned and potatoes are cooked. Cool 15 minutes before serving.