French Onion Scalloped Potatoes Recipe
This French Onion Scalloped Potatoes recipe combines sweet caramelized onions with thinly sliced russet potatoes baked in a rich Gruyère cheese sauce, topped with seasoned bread crumbs for a golden, crispy finish. Perfect as a comforting side dish for any occasion.
- Prep Time: 1 hour
- Cook Time: 1 hour
- Total Time: 2 hours
- Yield: 12 servings
- Category: Side Dish
- Method: Baking
- Cuisine: French
- Diet: Vegetarian
Ingredients
Units
Scale
Onions and Potatoes
- 4 sweet onions, thinly sliced
- 4 tablespoons unsalted butter
- kosher salt and pepper, to taste
- 1/2 teaspoon dried thyme
- 3 pounds russet potatoes, peeled and thinly sliced
Sauce
- 4 tablespoons unsalted butter
- 4 tablespoons all-purpose flour
- 3 1/2 cups milk
- kosher salt and pepper, to taste
- 1/4 teaspoon freshly grated nutmeg
- 12 ounces freshly grated Gruyère cheese, divided
- 1/3 cup seasoned bread crumbs
Instructions
- Preheat Oven: Preheat the oven to 375 degrees Fahrenheit to prepare for baking.
- Caramelize Onions: Heat 4 tablespoons of butter in a skillet over medium heat. Add the thinly sliced onions with a big pinch of salt and pepper. Cook for 10 minutes, stirring occasionally to soften. Reduce heat to medium-low, add dried thyme, and continue cooking for 30 to 40 minutes, stirring often until onions are golden and caramelized. Adjust heat or add water to prevent burning.
- Slice Potatoes: Use a mandoline or sharp knife to thinly and uniformly slice potatoes about ⅛ inch thick or thinner. To avoid browning, soak slices in ice water if not assembling immediately.
- Make Cheese Sauce: Melt remaining 4 tablespoons butter in a saucepan over medium heat. Whisk in the flour to form a roux and cook for 2 to 3 minutes until golden and fragrant. Slowly whisk in milk, stirring constantly. Add salt, pepper, and grated nutmeg. Reduce heat to low and stir in half of the Gruyère cheese until melted. Adjust seasoning to taste.
- Assemble Layers: Spread half of the potato slices evenly in a baking dish. Top with half the cheese sauce, then half the caramelized onions, and half of the remaining Gruyère. Repeat layers with remaining potatoes, cheese sauce, caramelized onions, and Gruyère. Sprinkle seasoned bread crumbs on top.
- Bake: Bake uncovered for 60 minutes or until potatoes are tender and easily pierced with a fork. If the top browns too quickly, tent with foil to prevent burning.
- Rest and Serve: Let the dish cool slightly before serving to allow the sauce to set and flavors to meld.
Notes
- Using a mandoline ensures thin, uniform potato slices for even cooking.
- Soaking potato slices in ice water prevents discoloration before baking.
- Adjust salt and pepper at various stages for balanced flavor.
- If Gruyère cheese is unavailable, Swiss cheese can be used as a substitute.
- To keep the top from burning, cover loosely with foil during the last 10-15 minutes of baking if necessary.
