Description
This classic Potatoes Au Gratin recipe features thinly sliced red potatoes and onions layered in a creamy cheese sauce made with cheddar and gruyere. Baked to golden perfection, it’s a comforting and elegant side dish perfect for family dinners or special occasions.
Ingredients
Scale
Potato and Onion Layers
- 2½ pounds red potatoes
- 1 medium onion (thinly sliced)
- ¾ teaspoon salt (divided)
- ½ teaspoon black pepper (divided)
Cheese Sauce
- 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
Instructions
- Preheat Oven: Preheat your oven to 400°F to prepare for baking the dish evenly and thoroughly.
- Prepare Potatoes and Onions: Wash the potatoes carefully and slice them into â…›-inch thin rounds. Slice the onion as thinly as possible to ensure even cooking and layering.
- Season and Layer: Season the sliced potatoes and onions with ½ teaspoon salt and ¼ teaspoon black pepper, tossing well to coat evenly. Form little stacks of potatoes and onions, then place these stacks on their sides in a greased casserole dish (2.5QT to 3QT size).
- Make Cheese Sauce: In a saucepan, melt the butter and whisk in the flour, cooking for 2 to 3 minutes to form a roux. Add the dry mustard powder, remaining ¼ teaspoon salt, remaining ¼ teaspoon black pepper, and milk. Whisk over medium heat until the sauce thickens and bubbles. Remove from heat and stir in the shredded cheddar and gruyere cheeses until fully melted and smooth.
- Assemble and Bake: Pour the warm cheese sauce over the potato stacks, gently separating them to let the sauce seep between layers. Cover with foil that has been sprayed with cooking spray to prevent sticking. Bake covered for 60 minutes.
- Finish Baking: Remove the foil and continue to bake uncovered for an additional 20 to 30 minutes, or until the top is lightly browned and the potatoes are tender and cooked through. Let the dish cool for 15 minutes before serving to allow the sauce to set.
Notes
- Use red potatoes for their waxy texture that holds up well when sliced thin and baked.
- Slicing potatoes uniformly ensures even cooking.
- Spraying the foil with cooking spray prevents the sauce from sticking to the foil during baking.
- Letting the dish rest before serving helps the cheese sauce thicken and enhances flavors.
- Gruyere adds a nutty flavor, but you can substitute with Swiss cheese if unavailable.
