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A bowl of crockpot French onion soup with melty cheese and croutons

Classic Crockpot French Onion Soup

Slow-cooked to perfection, this classic French onion soup features tender caramelized onions in a rich beef broth, topped with toasted baguette and melted Gruyère cheese.
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Prep Time 20 minutes
Cook Time 8 hours
Total Time 8 hours 20 minutes
Servings: 6 people
Calories: 350
Ingredients Equipment Method Notes

Ingredients
  

Main Ingredients
  • 5-6 pounds large yellow onions thinly sliced
  • 4 tablespoons butter
  • 4 cloves garlic minced
  • 6-8 cups high-quality beef broth low-sodium or unsalted
  • ½ cup dry white wine or dry sherry
  • 1 teaspoon Worcestershire sauce
  • 3-4 sprigs fresh thyme
  • 2 bay leaves
  • Salt and freshly ground black pepper to taste
Topping
  • 1 loaf baguette or crusty bread sliced ½ inch thick (stale is best)
  • 1-2 cups shredded Gruyère cheese Swiss or Provolone as alternatives

Equipment

  • Large Skillet or Dutch Oven
  • Slow Cooker
  • Baking Sheet
  • Oven-Safe Individual Crocks or Bowls
  • Oven Mitts

Method
 

Preparation
  1. Thinly slice all yellow onions evenly.
  2. Melt butter in a large skillet, add onions, and cook for 15-20 minutes until softened and light golden.
  3. Stir in minced garlic for one minute, then add wine or sherry, simmering for 2-3 minutes to deglaze and reduce alcohol.
Slow Cook
  1. Transfer sautéed onions and liquid to a slow cooker, then add beef broth, Worcestershire sauce, thyme, bay leaves, salt, and pepper.
  2. Cover and cook on LOW for 6-8 hours or HIGH for 3-4 hours until onions are tender and broth is rich.
  3. Remove thyme and bay leaves, then taste and adjust seasoning if needed.
Broil & Serve
  1. Preheat broiler and toast baguette slices on a baking sheet until golden brown.
  2. Ladle hot soup into oven-safe bowls, place toasted baguette on top, and generously sprinkle with Gruyère cheese.
  3. Broil for 2-4 minutes until cheese is melted, bubbly, and golden; watch carefully to prevent burning.
  4. Serve immediately, using oven mitts for hot bowls.

Notes

For best results, use good quality beef broth and allow ample time for the onions to caramelize slowly. Stale bread works best for toasting to prevent sogginess.