Description
This French Onion Soup Casserole is a comforting, hearty take on the classic French onion soup, featuring sweet Georgia-grown Vidalia onions slow-cooked to golden perfection, layered with toasted baguette slices, rich Gruyère cheese, and a flavorful beef broth and sherry sauce. Baked until bubbly and broiled to a perfect cheesy crust, this dish makes a delicious and warming meal for six.
Ingredients
Onion Mixture
- 1/4 cup unsalted butter
- 5 medium Vidalia onions, thinly sliced (about 3 lb.)
- 2 tsp. kosher salt
- 1/2 tsp. black pepper
- 3 thyme sprigs
- 2 flat-leaf parsley sprigs
- 2 bay leaves
Bread and Toppings
- 1 (16-oz.) baguette, thinly sliced
- 8 oz. Gruyère cheese, shredded (about 2 cups)
- 1 tsp. fresh thyme leaves
Sauce
- 1/3 cup all-purpose flour
- 3 cups reduced-sodium beef broth
- 1/2 cup sherry
Instructions
- Cook onions: Melt the butter in a Dutch oven over medium-low heat. Add the thinly sliced Vidalia onions, kosher salt, black pepper, thyme sprigs, parsley sprigs, and bay leaves. Stir frequently and cook the onions slowly until they become golden brown and caramelized, approximately 1 hour.
- Toast baguette slices: While the onions cook, preheat your oven to 350°F (175°C). Arrange the thinly sliced baguette pieces in a single layer on a baking sheet. Bake for about 12 minutes or until they are lightly toasted. Remove from the oven and set aside.
- Make sauce: Remove and discard the thyme, parsley sprigs, and bay leaves from the onion mixture. Sprinkle the flour over the onions and cook, stirring constantly, for 2 minutes to form a roux. Gradually add the reduced-sodium beef broth and sherry, stirring constantly. Bring the mixture to a boil over high heat and continue boiling, stirring, until it thickens slightly, around 2 to 3 minutes.
- Assemble casserole: In a 13- x 9-inch baking dish, layer half of the toasted baguette slices evenly. Spoon the onion and sauce mixture over the bread layer. Top evenly with the remaining toasted baguette slices. Sprinkle the shredded Gruyère cheese over the top. Cover the dish with aluminum foil.
- Bake casserole: Place the covered dish in the preheated oven and bake for 30 minutes to allow the flavors to meld and the casserole to heat through. Then, increase the oven setting to broil. Remove the foil and broil for approximately 3 minutes, or until the cheese is bubbly and golden brown. Remove from oven and sprinkle fresh thyme leaves on top before serving.
Notes
- Use Vidalia onions or any sweet onion variety for the best flavor in this recipe.
- To avoid burning the onions during the long cooking process, stir frequently and keep the heat at medium-low.
- Reduced-sodium beef broth is recommended to control saltiness, but regular beef broth can be used if preferred.
- Gruyère cheese is ideal for its creamy melt and nutty flavor, but Swiss or mozzarella can be substituted in a pinch.
- Serve this casserole with a simple green salad for a complete meal.
