French onion soup is about as classic as it’s possible for a dish to be, and there are few other soups that we find as satisfying, especially during the winter time. Still, as simple as it is, actually preparing and cooking it can be a time-consuming, tricky process, especially since the key element is cooking the onions slowly and carefully to caramelize them. What do if you’re craving the tasty soup but don’t have the time to stand over the stove? The answer, when you think about it, is obvious: get your slow cooker involved and let it worry for you! Here’s how to use it to make PERFECT French onion soup.

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French Onion Soup in Slow-Cooker


  • 3 pounds yellow onions, peeled, cut in half and thinly sliced
  • 2 tablespoons unsalted butter, melted
  • 2 tablespoons olive oil
  • 2 ½ teaspoons kosher salt
  • ½ teaspoon freshly ground black pepper, or more to taste
  • 2 sprigs fresh thyme
  • ¼ cup balsamic vinegar
  • 8 cups (2 32-ounce cartons) beef broth
  • ⅓ cup brandy, optional but recommended
  • 4 to 6 baguette slices, toasted (1 slice per bowl)
  • 1 ⅓ to 2 cups grated Gruyere cheese (⅓ cup per bowl)
  • Directions

    1. Put the onion slices in a 5-quart (or larger) slow cooker, along with the butter, olive oil, salt, and black pepper.
    2. Cover the crockpot and cook on low overnight, or for 10-12 hours. The onions should be dark golden brown and soft.
    3. Add the beef broth, balsamic vinegar, and fresh thyme.
    4. Cover and continue cooking on low for 6 to 8 hours.
    5. Season to taste with additional salt and pepper, if desired, and stir in the brandy, if using.
    6. Preheat the oven to 350 degrees Fahrenheit (180 degrees Celcius).
    7. In evenly-portioned amounts, ladle the soup into oven-safe bowls. Place the bowls on a baking sheet to catch any spills while in the oven.
    8. Top each bowl with a baguette slice and the shredded Gruyere.
    9. Bake for 20 to 30 minutes, until the cheese is completely melted.
    10. Turn the oven to broil and brown the tops for 2 to 3 minutes, or until the cheese is bubbling and browned. Remove from the oven and let cool for a few minutes before enjoying!

    Oh, this soup looks SO good, don’t you agree? We love having it do all the work while we take care of other things on our to-do lists. Have you ever made French onion soup in the slow cooker before? Do you have any tricks of your own for making the classic dish at home?