Description
This Creamy French Onion Casserole is a comforting and flavorful dish featuring caramelized onions enveloped in a rich, creamy cheese sauce, topped with a crispy parsley-bread crumb crust. Perfect as a hearty side or a vegetarian main, it combines classic French onion soup flavors into a warm, baked casserole that’s easy to prepare and sure to please.
Ingredients
Scale
Onion Mixture
- 6 medium onions, thinly sliced
- 2 tablespoons unsalted butter
- 1 tablespoon olive oil
- 1 teaspoon sugar
- 1/4 teaspoon salt
- 1/4 teaspoon black pepper
- 4 cloves garlic, minced
- 1/4 cup all-purpose flour
- 1 cup beef broth
- 1 cup heavy cream
- 1/2 cup grated Gruyère cheese
- 1/2 cup grated Parmesan cheese
- 1 teaspoon dried thyme
Topping
- 1 1/2 cups bread crumbs
- 2 tablespoons fresh parsley, chopped
Instructions
- Preheat Oven: Preheat your oven to 350°F (175°C) to prepare for baking the casserole later.
- Heat Butter and Oil: In a large skillet, melt the butter and warm the olive oil over medium heat to create the base for cooking the onions.
- Caramelize Onions: Add the thinly sliced onions along with sugar, salt, and black pepper. Cook over medium-low heat, stirring occasionally, for about 30 to 35 minutes until the onions become golden brown and caramelized, which builds the dish’s deep flavor.
- Add Garlic: Stir in the minced garlic and cook for an additional 2 minutes until the garlic is fragrant, enhancing the savory aroma.
- Incorporate Flour: Sprinkle the all-purpose flour evenly over the onion mixture and stir thoroughly to incorporate. This step helps to thicken the sauce.
- Add Liquids and Thicken: Gradually pour in the beef broth and heavy cream while stirring continuously. Cook for 5 to 7 minutes until the mixture thickens to a creamy consistency.
- Melt Cheeses: Remove the skillet from heat and stir in the grated Gruyère and Parmesan cheeses until fully melted and combined for added richness and flavor.
- Add Seasoning: Stir in the dried thyme to infuse the casserole with a fragrant herbal note.
- Transfer to Casserole Dish: Pour the onion and cheese mixture into a greased casserole dish, spreading it evenly.
- Prepare Topping: In a separate bowl, mix the bread crumbs with the chopped fresh parsley. Spread this mixture evenly over the surface of the casserole to create a crunchy topping.
- Bake: Place the casserole in the preheated oven and bake for 20 to 25 minutes until the top is golden brown and bubbly, indicating it’s heated through and topping is crisp.
- Cool and Serve: Let the casserole cool for a few minutes before serving to allow it to set slightly for easier portioning.
Notes
- For a vegetarian variation, substitute beef broth with vegetable broth.
- Gruyère cheese can be replaced with Swiss cheese if unavailable.
- Use day-old bread for bread crumbs for better texture.
- Caramelizing onions slowly over medium-low heat is key for developing deep flavor—do not rush this step.
- Optionally, garnish with additional fresh parsley for a fresh finish.
