Name: Potatoes Au Gratin
Prep time: 20 min
Cook time: 90 min
Total time: 125 min
Yield: 8 servings
Ingredients: 2½ pounds red potatoes; 1 medium 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)

Before You Begin

Potatoes au gratin combines thin slices of red potato and onion with a cheddar and Gruyère sauce. Arrange the slices in small stacks on their sides so the sauce can reach between the layers.

Start the casserole covered with foil, then uncover it to brown the top and finish cooking the potatoes. Allow 15 minutes of cooling before serving this side dish, which makes eight portions.

Use a greased 2½- to 3-quart casserole dish and heat the oven to 400°F.

Slice the potatoes ⅛ inch thick and the onion as thinly as possible.

Allow 60 minutes covered baking, another 20–30 minutes uncovered, and 15 minutes cooling before serving.

8 servings · 10 ingredients. Adapted from Spend With Pennies. The source lists 20 minutes prep, 90 minutes cooking, and 2 hours 5 minutes total, including the 15-minute cooling period. The method gives a baking range of 60 minutes covered plus 20–30 minutes uncovered; check that the potatoes are cooked through before taking the dish out.

Cooking Steps

Heat the oven
Preheat the oven to 400°F.
Slice the potatoes and onion
Wash the potatoes and cut them into ⅛-inch slices. Slice the onion as thinly as possible.
Season and arrange the stacks
Toss the potatoes and onions with ½ teaspoon salt and ¼ teaspoon black pepper until evenly coated. Make small stacks of the slices and set the stacks on their sides in a greased 2½- to 3-quart casserole dish.
Make the cheese sauce
Melt the butter in a saucepan, add the flour, and cook together for 2–3 minutes. Add the mustard powder, remaining ¼ teaspoon salt, remaining ¼ teaspoon black pepper, and milk. Whisk over medium heat until thick and bubbling. Remove the pan from the heat and stir in the cheddar and Gruyère until melted.
Add the sauce and bake covered
Pour the cheese sauce over the potatoes. Gently separate the stacks so the sauce runs between the slices. Spray the foil with cooking spray, cover the dish with it, and bake for 60 minutes.
Brown and rest
Remove the foil and bake for another 20–30 minutes, until the top is lightly browned and the potatoes are cooked through. Let the casserole cool for 15 minutes before serving.

Recipe Notes

Keep the slices thin

Aim for the ⅛-inch potato slices in the method and slice the onion as thinly as possible. The sauce needs to reach between the stacks, so separate them gently as you pour it in.

Cheese and optional additions

The source recommends shredding cheese from a block. Fresh thyme or rosemary and garlic can be added to the sauce if desired. You can also sprinkle extra cheddar or Parmesan on top after removing the foil.

Optional microwave head start

To shorten the oven time, the source suggests arranging the potatoes in a microwave-safe casserole dish before adding the sauce, covering with plastic wrap suitable for microwave use, and microwaving on full power for about 10 minutes. Carefully remove the hot wrap, add the cheese sauce, and bake as directed for about 45–55 minutes. Use only a dish and cover suitable for the appliances involved.

Store and reheat

Refrigerate leftovers in an airtight container for up to 4 days. Reheat in the oven or microwave.

Spare Hours · sparehours.puzzlegames.app/recipes/potatoes-au-gratin/ · Recipe source: https://www.spendwithpennies.com/au-gratin-potatoes/

Recipe Source

Adapted from Spend With Pennies: Potatoes Au Gratin. Ingredient amounts, method details and source time estimates come from the supplied recipe record. The instructions have been rewritten for this page.

The food image is an illustration supplied in this collection, derived from the source recipe photograph. Image credits