Slow Cooker French Onion Soup


  • 4 medium onions, sliced
  • 3 tablespoons melted butter
  • 9 cups low sodium beef broth (two 900ml boxes)
  • 2 tablespoons balsamic vinegar
  • 3 tablespoons sherry or brandy (optional)
  • 8 slices sliced baguette or French bread
  • olive oil
  • 1 cup grated Gruyère cheese (1/4 cup per bowl)
  • salt and pepper to taste


Place sliced onions, melted butter, salt and pepper into the slow cooker and cook on LOW, overnight, until onions are dark, golden brown

Stir in the broth and balsamic vinegar, then cover and cook for LOW for another 6 to 8 hours. Place a towel over the lid if too much steam escapes.

1 Hour Before Serving

Preheat oven to 350°F.  Arrange the sliced baguette on a baking sheet. Drizzle olive oil over the bread slices, then flip them over and drizzle more oil on the other side. Toast bread 15 minutes, then turn over and bake the other side for another 15 minutes.

Taste the soup. Season with more salt and pepper if needed, then stir in sherry or brandy if using.

Ladle the soup and onions into oven-safe soup bowls and place the bowls on a baking sheet. Top each bowl with toasted bread and shredded cheese, about ¼ cup per bowl.

If you don’t have individual bowls, put the soup in a casserole dish or attractive-looking pot, and put all the bread and cheese and top. When it comes time to serve, just put the pot on the table, and serve the soup into individual bowls.

Bake for 20 to 30 minutes, until the cheese is almost melted, then broil for 2-3 minutes more to make the cheese brown and bubbly.

Remove from the oven, let cool for a few minutes, then serve.

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