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Slow Cooker French Onion Soup with Gruyère Toast Recipe

5 Stars 4 Stars 3 Stars 2 Stars 1 Star 4.3 from 57 reviews
  • Author: Mary
  • Prep Time: 0h 20m
  • Cook Time: 6h 0m
  • Total Time: 6h 20m
  • Yield: 6 servings
  • Category: Soup
  • Method: Slow Cooking
  • Cuisine: French

Description

A rich and comforting Slow Cooker French Onion Soup featuring caramelized onions, savory broths, and topped with toasted baguette slices and melted Gruyère cheese. Perfect for a cozy meal with minimal hands-on cooking.


Ingredients

Scale

Soup Ingredients

  • 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

Topping Ingredients

  • 1 baguette, sliced into 1-inch pieces
  • 2 cups grated Gruyère cheese


Instructions

  1. Prepare onions and garlic: Peel and thinly slice the onions into even rings and mince the garlic cloves thoroughly.
  2. Caramelize onions and garlic: Heat olive oil in a large skillet over medium-high heat. Add sliced onions and garlic, sautéing while stirring regularly until onions turn golden brown and caramelized, approximately 15-20 minutes.
  3. Combine in slow cooker: Transfer the caramelized onions and garlic into the slow cooker. Pour in beef broth, chicken broth, dry white wine, and Worcestershire sauce.
  4. Add herbs and seasonings: Add fresh thyme sprigs and bay leaf to the slow cooker mixture. Season with salt and pepper to taste.
  5. Slow cook the soup: Cover and cook on low for 6 to 8 hours or on high for 3 to 4 hours until flavors meld beautifully.
  6. Remove herbs: Once cooking is complete, take out the thyme sprigs and bay leaf from the soup.
  7. Toast baguette slices: Preheat oven to 400°F (200°C). Arrange baguette slices on a baking sheet and toast in the oven until golden and crisp, around 5-7 minutes.
  8. Assemble soup bowls: Ladle hot soup into oven-safe bowls placed on a rimmed baking sheet. Top each bowl with a toasted baguette slice and generously sprinkle Gruyère cheese over the top.
  9. Broil cheese topping: Place the baking sheet with soup bowls under the oven broiler and cook until the cheese melts and bubbles, about 3-5 minutes.
  10. Serve: Carefully remove from oven, garnish with fresh thyme if desired, and serve the soup hot for a cozy, flavorful meal.

Notes

  • For a vegetarian version, substitute beef and chicken broth with vegetable broth and omit Worcestershire sauce or use a vegetarian alternative.
  • Ensure onions are evenly sliced to cook uniformly and caramelize properly.
  • Use oven-safe bowls when broiling the cheese to avoid damage or injury.
  • Gruyère cheese can be substituted with Swiss cheese if needed, though it will alter the flavor slightly.
  • Leftover soup can be refrigerated for up to 3 days and reheated gently on the stovetop.