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Close up of Slow Cooker French Onion Soup
Michonne Zendaya

Slow Cooker French Onion Soup

This slow cooker French onion soup is rich, savory, and topped with cheesy toasted bread. Caramelized onions simmer slowly in broth for a comforting, restaurant-quality classic made easy at home.
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Prep Time 15 minutes
Cook Time 8 hours
Total Time 8 hours 15 minutes
Servings: 6 bowls
Course: Main Course, Soup
Cuisine: French
Calories: 360
Ingredients Equipment Method Notes

Ingredients
  

  • 4 large yellow onions, thinly sliced
  • 3 tbsp unsalted butter
  • 2 tbsp olive oil
  • 2 cloves garlic, minced
  • 8 cups beef broth
  • 0.5 cup dry white wine (optional)
  • 2 tsp dried thyme (or 1 tbsp fresh thyme)
  • 1 tsp salt
  • 0.5 tsp black pepper
  • 6 slices French bread, toasted
  • 1.5 cups grated Gruyère cheese

Equipment

  • slow cooker
  • Large skillet
  • wooden spoon
  • oven-safe soup bowls
  • broiler
  • ladle

Method
 

  1. In a large skillet, melt butter with olive oil over medium heat. Add onions and cook, stirring often, until caramelized, about 20 minutes.
  2. Add garlic and cook for 1 minute. Transfer onion mixture to the slow cooker.
  3. Stir in beef broth, wine (if using), thyme, bay leaves, salt, and pepper. Cover and cook on low for 8 hours.
  4. Remove bay leaves. Ladle soup into oven-safe bowls.
  5. Top each bowl with a toasted bread slice and sprinkle generously with Gruyère cheese.
  6. Broil until cheese is melted and bubbly. Serve hot.

Notes

Use yellow or sweet onions for the best flavor. Toast bread slices separately, then top with cheese and broil until bubbly before serving over soup.