Description
Potatoes Au Gratin is a classic French-inspired casserole featuring thinly sliced red potatoes layered with onions and smothered in a rich, creamy cheese sauce made from cheddar and gruyere. This comforting dish is baked to golden perfection, making it a perfect side for family dinners or special occasions.
Ingredients
Scale
Vegetables
- 2½ pounds red potatoes
- 1 medium onion (thinly sliced)
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
- ¾ teaspoon salt (divided)
- ½ teaspoon black pepper (divided)
Instructions
- Preheat Oven: Preheat your oven to 400°F to ensure it reaches the right temperature for baking the potatoes au gratin evenly and thoroughly.
- Prepare Vegetables: Wash the red potatoes thoroughly and slice them into very thin â…›-inch slices to ensure they cook evenly. Thinly slice the onion as well to layer with the potatoes.
- Season and Layer: In a mixing bowl, season the potato and onion slices with ½ teaspoon salt and ¼ teaspoon black pepper. Toss them to coat evenly. Then, create little stacks alternating potatoes and onions, and stand these stacks on their side inside a greased 2.5 to 3-quart casserole dish.
- Make Cheese Sauce: In a saucepan, melt butter over medium heat and whisk in the flour, cooking it for 2 to 3 minutes to form a roux. Stir in dry mustard powder, remaining ¼ teaspoon salt, and ¼ teaspoon pepper. Gradually add the milk while whisking, cooking until the sauce thickens and bubbles. Remove from heat and stir in the shredded cheddar and gruyere cheeses until melted and smooth.
- Combine and Bake: Pour the creamy cheese sauce over the layered potatoes, gently separating the stacks to allow sauce to seep between layers. Cover the dish with foil sprayed with cooking spray to prevent sticking. Bake covered for 60 minutes at 400°F.
- Finish Baking: Remove the foil carefully and continue baking for an additional 20 to 30 minutes to allow the top to brown lightly and the potatoes to become tender and fully cooked.
- Cool and Serve: Let the dish cool for about 15 minutes to set before serving. This resting time enhances the flavors and makes it easier to portion.
Notes
- For a creamier texture, you can add a splash of heavy cream to the cheese sauce.
- Use a mandoline slicer for perfectly thin and even potato and onion slices.
- To avoid sticking, ensure the casserole dish is greased well before layering.
- Let the dish rest after baking to allow the sauce to thicken and meld with the potatoes.
- Leftovers can be refrigerated for up to 3 days and reheated in the oven covered to retain moisture.
