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Easy Slow Cooker French Onion Soup

This easy slow cooker French onion soup is packed with caramelized onions and a rich beefy broth, topped with melty cheese.
Prep : 10 Total : 25 minutes
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Ingredients
  

Main Ingredients

  • 6 large sweet onions thinly sliced
  • 4 tablespoons unsalted butter melted
  • 0.25 teaspoon sugar
  • 0.5 teaspoon salt
  • 0.5 teaspoon fresh ground black pepper
  • 6 sprigs fresh thyme
  • 1 bay leaf
  • 6 cups low sodium beef broth
  • 0.5 cup dry white wine

Optional Toppings

  • 6 slices French bread
  • 1.5 cups shredded Gruyere cheese

Instructions
 

Preparation Steps

  • Caramelize the onions. Place sliced onions in a 6-quart slow cooker. Stir in the melted butter, sugar, salt, and pepper. Top with thyme sprigs and bay leaf. Place the lid on the pot and cook on LOW for 8 hours, or until the onions are deeply browned and caramelized. Stir halfway through.
  • Make it soupy. Once onions are caramelized, stir in the beef broth and white wine. Taste for salt and pepper and season accordingly.
  • Cook. Cover and cook on LOW for an additional 4 hours or on HIGH for 2 hours, until heated through.
  • Ladle into bowls. Remove the lid and discard the thyme sprigs and bay leaf. Ladle the soup into ovenproof bowls and transfer the bowls to a large baking sheet.
  • Add toppings. Top each bowl of soup with a slice of French bread (if using) and shredded Gruyere cheese (if using).
  • Melt the cheese. Turn the oven broiler to High. Broil the soups in the oven until the cheese is melted and bubbly, about 2 to 3 minutes. Watch carefully to prevent burning.
  • Serve. Carefully remove from oven and enjoy immediately.

Notes

For an even richer flavor, you can use a combination of beef broth and chicken broth. If you don't have dry white wine, you can substitute it with a little more beef broth.