French Onion au Gratin Potatoes

Course: Side Dish

Cuisine: French / American

Prep Time: 20

Cook Time: 1 40

Resting Time: 15

Total Time: 2 15

Servings:

Calories: 413kcal

Author: Kris Longwell

Rich, creamy, and loaded with caramelized onions and melted cheese, these French Onion Au Gratin Potatoes make a comforting and elegant side dish perfect for any special meal.

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Equipment

Large pot or skillet for caramelizing onions (8-quart Dutch oven is excellent)
9"x13" baking dish or similar size baking dish or 12-inch cast-iron skillet

Ingredients

4 tablespoon unsalted butter
4 large yellow onions or 5 medium, peeled and thinly sliced
4 cloves garlic minced
1 teaspoon dried thyme or 1 tablespoon fresh
¼ cup white wine optional, see NOTES
3 tablespoon all-purpose flour
2 cups beef stock or broth
1 cup heavy cream or half and half
salt and pepper
1 tablespoon oil or butter, for greasing dish
2½ lbs gold potatoes peeled and thinly sliced (⅛" inch)
¼ cup Parmesan cheese grated
1 cup Gruyère cheese shredded
fresh thyme chopped, for garnish (optional)

Instructions

In a large skillet, pot, or Dutch oven, melt the butter over medium heat. Add the onions, and cook, stirring often, until deep golden brown, and caramelized - about 40 to 50 minutes. Stir in the garlic and thyme and cook, stirring often, for another minute.
4 tablespoon unsalted butter, 4 large yellow onions, 4 cloves garlic, 1 teaspoon dried thyme
Add the wine (if using) and stir until mostly evaporated, usually about 1 minute. Stir in the flour to coat the onions and cook, stirring often, for another 1 to 2 minutes.
¼ cup white wine, 3 tablespoon all-purpose flour
Whisk in the beef stock and cream. Gently stir with a wooden spoon or spatula until slightly thickened, about 3 to 4 minutes. Stir in 1 teaspoon salt and ½ teaspoon black pepper. Remove from the heat.
2 cups beef stock, 1 cup heavy cream, salt and pepper
Preheat oven to 375°F.
Grease your dish with softened butter or olive oil. Arrange a double layer of potatoes in the greased dish. Sprinkle salt and pepper over the potatoes. Spoon a thin layer of the sauce over the potatoes (you'll do about a quarter of the sauce). Sprinkle Parmesan cheese over the sauce. Repeat this process 3 to 4 more times (until you run out of potatoes, or sauce, whichever comes first).
1 tablespoon oil, 2½ lbs gold potatoes, ¼ cup Parmesan cheese
Top the dish with the shredded Gruyère. Cover with foil and bake in the preheated oven (375°F) for 45 minutes. Remove the foil and bake for another 20 minutes, or until the cheese has browned in spots.
1 cup Gruyère cheese
Remove the dish from the oven and let rest for 10 to 15 minutes. Or, cover with foil and let rest for up to 30 minutes. Garnish with chopped fresh herbs (ie, thyme), if desired. Serve immediately.
fresh thyme

Video

Notes

NOTE: Watch the video in the recipe card for visual guidance.

For best flavor, use dry white wine, but it can be omitted or replaced with extra broth or a splash of vinegar.
Store leftovers in an airtight container in the refrigerator for up to 3 days. Reheat gently in the oven until warmed through.
This dish freezes well—cool completely, then freeze in an airtight container for up to 2 months. Thaw overnight in the fridge before reheating. The texture may be a little grainy after thawing, but will still be delicious after reheating.
Use thinly sliced potatoes for even cooking and a creamy texture.
Freshly shredded cheese melts better than pre-shredded varieties.

Nutrition