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Slow Cooker French Onion Soup

A warm bowl of Slow Cooker French Onion Soup featuring caramelized onions, rich broth, and melted cheese, perfect for a cozy evening.
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Prep Time 10 minutes
Cook Time 8 hours
Total Time 8 hours 10 minutes
Servings: 6 servings
Course: Appetizer, Soup
Cuisine: French
Calories: 300
Ingredients Method Notes

Ingredients
  

Main Ingredients
  • 4 large large yellow onions, thinly sliced Yellow and sweet onions work best for caramelizing.
  • 4 tablespoons unsalted butter Melted for sautéing onions.
  • 5 cups beef or vegetable broth Use vegetable broth for a vegetarian version.
  • 1 teaspoon salt
  • 1 teaspoon sugar
  • 1 teaspoon dried thyme
  • 1 leaf bay leaf For extra flavor.
  • to taste freshly ground black pepper
  • 1 loaf French bread or baguette, sliced For serving.
  • 1-2 cups grated gruyère or mozzarella cheese For topping.

Method
 

Preparation
  1. In a skillet, melt the butter over medium heat. Add the thinly sliced onions and cook for about 10 minutes, stirring occasionally, until they become soft and golden brown.
  2. Place the caramelized onions into the slow cooker. If you've burnt a few, don’t worry—just call them 'extra flavor'!
  3. Pour in the beef or vegetable broth, salt, sugar, thyme, and black pepper. Toss in the bay leaf for extra flavor.
  4. Cover and cook on low for 6-8 hours, or on high for 3-4 hours. In the final hour of cooking, taste and adjust the seasoning if needed.
  5. When ready to serve, toast slices of French bread until golden brown.
  6. Ladle the hot soup into bowls, place a slice of toasted bread on top, and generously sprinkle with grated cheese. Pop under the broiler for a few minutes until the cheese is bubbly and golden.
  7. Allow it to cool slightly, then dig in.

Notes

Store leftovers in an airtight container in the refrigerator for up to 3 days or freeze for up to 3 months. Reheat on the stove over low heat and re-toast bread before serving for best results.