Description
This Creamy French Onion Casserole is a comforting and flavorful dish featuring caramelized onions cooked in a rich, creamy sauce with Gruyère and Parmesan cheeses, topped with a crunchy parsley-breadcrumb crust. Perfect as a side dish or a hearty vegetarian main, it brings the classic French onion soup flavors into a delicious baked casserole form.
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
Sauce
- 1/4 cup all-purpose flour
- 1 cup beef broth
- 1 cup heavy cream
Cheese and Herbs
- 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 the oven: Begin by preheating your oven to 350°F (175°C) to prepare for baking the casserole later.
- Heat butter and oil: In a large skillet, melt the unsalted butter with olive oil over medium heat until fully combined and hot.
- Caramelize the onions: Add the thinly sliced onions, sugar, salt, and pepper to the skillet. Cook on medium-low heat, stirring occasionally, until the onions turn golden brown and caramelized, about 30 to 35 minutes.
- Add garlic: Stir in the minced garlic and cook for an additional 2 minutes until it becomes fragrant, enhancing the flavor.
- Thicken with flour: Sprinkle the all-purpose flour evenly over the onion mixture and stir thoroughly to incorporate the flour into the onions.
- Make the creamy sauce: Gradually pour in the beef broth and heavy cream while continuously stirring. Continue cooking until the mixture thickens, about 5 to 7 minutes.
- Add cheeses: Remove the skillet from heat and stir in the grated Gruyère and Parmesan cheeses until they melt smoothly into the sauce.
- Season with thyme: Mix in the dried thyme to infuse the casserole with aromatic herbal notes.
- Transfer to casserole dish: Pour the entire onion and cheese mixture into a greased casserole dish, spreading it evenly.
- Prepare the topping: In a separate bowl, combine the bread crumbs with fresh chopped parsley, then evenly sprinkle this mixture over the top of the casserole.
- Bake the casserole: Place the casserole dish in the preheated oven and bake for 20 to 25 minutes until the topping turns golden brown and bubbly.
- Cool and serve: Allow the casserole to cool for a few minutes before serving to let it set slightly for the best texture.
Notes
- Caramelizing the onions slowly is key to developing a deep, sweet flavor without burning.
- Be sure to stir frequently when adding the flour, broth, and cream to avoid lumps.
- Using Gruyère cheese adds a rich, slightly nutty flavor; you can substitute with Swiss cheese if needed.
- The breadcrumb topping adds a delightful crunch, but you can omit it for a softer texture.
- This casserole pairs wonderfully with roasted meats or can be enjoyed as a vegetarian main dish.
