Description
Hearty French onion soup casserole combines classic French bistro flavors with comforting casserole magic. Caramelized onions, rich beef broth, and melted Gruyère cheese create a soul-warming dish you’ll crave on chilly evenings.
Ingredients
Scale
Main Ingredients:
- 5 medium Vidalia onions, thinly sliced (about 1.36 kilograms)
- 1 (16-ounce) baguette, thinly sliced
- 8 ounces (226 grams) Gruyère cheese, shredded (about 2 cups)
Liquid and Flavoring Ingredients:
- 3 cups reduced-sodium beef broth
- ½ cup sherry
- ¼ cup unsalted butter
Seasoning and Herbs:
- 2 teaspoons kosher salt
- ½ teaspoon black pepper
- 3 thyme sprigs
- 2 flat-leaf parsley sprigs
- 2 bay leaves
- ⅓ cup all-purpose flour
- 1 teaspoon fresh thyme leaves
Instructions
- Caramelize onions in a Dutch oven by melting butter over medium-low heat. Add sliced onions, salt, black pepper, fresh thyme sprigs, parsley sprigs, and bay leaves. Gently stir and cook for approximately 60 minutes until onions develop a rich, golden-brown color.
- Preheat the oven to 350°F (175°C). Arrange baguette slices in a single layer on a baking sheet. Toast the bread for 12 minutes until light golden and crisp, then set aside.
- Remove and discard thyme and parsley sprigs and bay leaves from the caramelized onion mixture. Sprinkle all-purpose flour into the onions, stirring continuously for 2 minutes to prevent burning.
- Pour beef broth and dry sherry into the onion mixture. Increase heat to high and bring to a boil, stirring constantly until the sauce thickens slightly, about 2-3 minutes.
- Grease a 13 x 9-inch (33 x 23 centimeters) baking dish. Create the first layer by evenly arranging half of the toasted baguette slices across the bottom.
- Spread the onion and broth mixture uniformly over the first bread layer. Top with remaining baguette slices to create a second layer.
- Generously sprinkle shredded Gruyère or Swiss cheese over the top. Cover the dish completely with aluminum foil.
- Bake in the preheated oven for 30 minutes. Remove foil and switch oven to broil. Broil for 3 minutes until cheese becomes bubbly and slightly golden.
- Garnish with freshly chopped thyme leaves before serving. Allow the casserole to cool for 5 minutes to set the layers.
Notes
- Slow-cooking onions creates deep, rich flavor that’s essential to the soup’s character, transforming humble ingredients into a luxurious dish.
- Toasting baguette slices beforehand ensures a crispy texture that holds up against the savory onion sauce without becoming soggy.
- Using a combination of broth and sherry adds complexity and depth, elevating the traditional French onion soup profile.
- Layering bread and onion mixture allows each bite to capture the perfect balance of crispy and tender elements.
- Covering the casserole during initial baking prevents excessive drying while allowing flavors to meld together seamlessly.
- Finishing under the broiler creates a golden, bubbly cheese crust that mimics the classic French onion soup gratinée style.
- Prep Time: 1 hour 20 minutes
- Cook Time: 45 minutes
- Category: Dinner, Appetizer
- Method: Baking
- Cuisine: French
Nutrition
- Serving Size: 8
- Calories: 370 kcal
- Sugar: 6 g
- Sodium: 620 mg
- Fat: 22 g
- Saturated Fat: 12 g
- Unsaturated Fat: 8 g
- Trans Fat: 0.5 g
- Carbohydrates: 32 g
- Fiber: 3 g
- Protein: 15 g
- Cholesterol: 55 mg