Potatoes Au Gratin

By spend with pennies

Ingredients

2 ½ pounds red potatoes
1 onion (thinly sliced)
3 tablespoons butter
3 tablespoons all-purpose flour
1 teaspoon dry mustard powder
2 cups milk
1 cup shredded cheddar cheese
½ cup shredded gruyere cheese
¾ teaspoon salt (divided)
½ teaspoon black pepper (divided)

Prep Time20mins
Cook Time90mins
Servings8

Instructions

Preheat oven to 400°F.

Wash potatoes and slice into " thin slices. Slice onion as thin as possible.

Season 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.

Melt 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.

Pour 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.

Remove foil and bake an additional 20 to 30 minutes or until lightly browned and potatoes are cooked. Cool 15 minutes before serving.