Description
This Slow Cooker French Onion Soup recipe transforms simple ingredients into a rich, comforting meal perfect for chilly days. Sweet caramelized onions, savory beef and chicken broth, and a touch of white wine create a deeply flavorful base. Topped with toasted baguette slices and melted Gruyère cheese, this classic French dish uses the slow cooker for effortless, slow-simmered perfection.
Ingredients
Scale
Sauce and Soup Base
- 4 large yellow onions, thinly sliced
- 4 cloves garlic, minced
- 2 tablespoons olive oil
- 4 cups beef broth
- 2 cups chicken broth
- 1/2 cup dry white wine
- 1 tablespoon Worcestershire sauce
- 4 sprigs fresh thyme
- 1 bay leaf
- Salt and pepper, to taste
Toppings
- 1 baguette, sliced into 1-inch pieces
- 2 cups grated Gruyère cheese
Instructions
- Prepare Onions and Garlic: Peel and thinly slice the yellow onions into even rings. Mince the garlic cloves finely to be ready for sautéing.
- Caramelize Onions and Garlic: Heat olive oil in a large skillet over medium-high heat. Add the sliced onions and minced garlic, stirring frequently. Continue cooking for 15-20 minutes until the onions are deeply caramelized and golden brown, developing sweet flavor and rich color.
- Transfer to Slow Cooker: Move the caramelized onions and garlic into the slow cooker pot to begin slow simmering the soup flavors.
- Add Broth and Flavorings: Pour in beef and chicken broth along with the dry white wine and Worcestershire sauce. Add fresh thyme sprigs and the bay leaf. Season with salt and pepper according to your taste.
- Slow Cook the Soup: Cover the slow cooker. Cook on low for 6 to 8 hours or on high for 3 to 4 hours, allowing the flavors to meld and deepen slowly.
- Remove Herbs: Once cooking is complete, remove and discard the thyme sprigs and bay leaf from the soup.
- Toast Baguette Slices: Preheat your oven to 400°F (200°C). Arrange the baguette slices on a baking sheet and toast for 5-7 minutes until they are golden and crisp.
- Assemble for Broiling: Ladle the hot soup into oven-safe bowls set on a rimmed baking sheet. Top each bowl with a toasted baguette slice, then generously sprinkle with grated Gruyère cheese.
- Broil for Cheese Melt: Place the baking sheet under the oven broiler. Broil for 3-5 minutes until the cheese melts completely, bubbles, and turns golden brown.
- Serve: Carefully remove bowls from the oven. Optionally garnish with fresh thyme sprigs and serve the soup hot, enjoying the comforting layers of flavor and texture.
Notes
- Caramelizing onions slowly is key for depth of flavor, so do not rush this step.
- If you prefer a vegetarian version, substitute vegetable broth and omit Worcestershire sauce or use a vegetarian alternative.
- Gruyère cheese is traditional, but Swiss or Emmental can be used as substitutes.
- Use oven-safe bowls for broiling to avoid any risk of breaking or melting.
- Leftover soup can be refrigerated up to 3 days or frozen for up to 1 month.
