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I love this recipe because I fool guests into thinking I slaved away for hours in the kitchen


French onion soup is a beloved classic that graces the menus of fine restaurants around the world. With its rich, caramelized onions, savory broth, and cheesy topping, it’s a comfort food that warms the soul. Traditionally, making French onion soup can be a time-consuming process, involving hours of carefully watching over a stovetop to achieve the perfect caramelization. However, there’s a more convenient way to enjoy this delightful dish at home: by using a slow cooker. This method allows you to set it and forget it, giving you all the deep, complex flavors of a traditional French onion soup with minimal effort. In this article, we’ll guide you through a simple yet delicious slow cooker French onion soup recipe that will become a staple in your home.

Ingredients and Preparation


To create this delectable slow cooker French onion soup, you will need the following ingredients:

  • 4 large onions: Sliced
  • 2 tablespoons butter
  • 1 teaspoon sugar
  • 2 quarts beef broth: No sodium added
  • 1/4 cup sherry
  • 2 sprigs fresh thyme
  • 1 1/2 teaspoons salt
  • Pepper: To taste
  • Sliced bread of choice (or croutons)
  • 8 ounces Gruyere cheese: Sliced (Swiss cheese can be substituted)

Equipment Needed

  • 6-quart slow cooker
  • Knife and cutting board
  • Ovenproof mugs or bowls
  • Broiler (optional)

Instructions for Making Slow Cooker French Onion Soup

Step 1: Prepare the Onions

Begin by slicing four large onions. The key to a great French onion soup is to cut the onions into uniform slices to ensure even cooking. Place the sliced onions into the bottom of a 6-quart slow cooker.

Step 2: Add Butter, Sugar, and Salt

Add 2 tablespoons of butter, 1 teaspoon of sugar, and 1 1/2 teaspoons of salt to the slow cooker with the onions. The sugar helps to enhance the caramelization process, while the butter adds richness.

Step 3: Slow Cook the Onions

Cover the slow cooker and cook the onions on high for 7 hours, or until they are soft and brown. This long cooking time allows the onions to develop a deep, caramelized flavor that is essential for authentic French onion soup.

Step 4: Add Broth, Sherry, and Thyme

After the onions are beautifully caramelized, add 2 quarts of no sodium added beef broth, 1/4 cup of sherry, 2 sprigs of fresh thyme, and pepper to taste. Cover the slow cooker and continue to cook on high for an additional hour. This step melds all the flavors together, creating a rich and savory broth.

Step 5: Prepare the Toppings

While the soup is finishing in the slow cooker, prepare your toppings. Slice your bread of choice or use croutons. For an authentic touch, use French baguette slices. Slice 8 ounces of Gruyere cheese (or Swiss cheese if you prefer).

Step 6: Serve the Soup

To serve, ladle the soup into ovenproof mugs or bowls. Place a slice of bread (or croutons) on top of each serving. Add a generous slice of Gruyere cheese over the bread. For an extra cheesy experience, broil the mugs under a broiler for a few minutes until the cheese is bubbly and golden brown.

Step 7: Optional Cheese Melting

For those who love their cheese extra melty, cook the soup with the cheese topping for an additional 15 minutes in the slow cooker before serving. This will allow the cheese to melt further into the soup, enhancing its flavor and texture.

Tips for the Perfect French Onion Soup

Tip 1: Use the Right Onions

Yellow onions are traditionally used for French onion soup because of their balance of sweetness and savory flavor. However, feel free to experiment with different types of onions, such as white or red, for a unique twist.

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Tip 2: Choose Quality Broth

The quality of the broth can make or break your soup. Using a no-sodium added beef broth allows you to control the saltiness of the final dish. For an even richer flavor, consider making your own beef broth at home.

Tip 3: Enhance with Herbs

Fresh thyme is a classic herb for French onion soup, but you can also experiment with adding a bay leaf or a sprig of rosemary for additional depth of flavor.

Tip 4: Wine Substitutes

If you don’t have sherry on hand, you can substitute with a dry white wine or even a splash of balsamic vinegar. These alternatives will still provide the necessary acidity to balance the sweetness of the onions.

Tip 5: Make Ahead and Store

French onion soup can be made ahead of time and stored in the refrigerator for up to three days. Simply reheat and add the bread and cheese topping when you’re ready to serve.

Frequently Asked Questions (FAQs)

Q: Can I use a different type of cheese?

A: Yes, while Gruyere is the traditional choice for French onion soup, you can substitute it with Swiss, Emmental, or even a sharp cheddar if you prefer.

Q: Can I make this recipe vegetarian?

A: Absolutely. You can use vegetable broth instead of beef broth to make a vegetarian version of French onion soup. Just ensure the broth is rich and flavorful.

Q: How can I prevent my onions from burning in the slow cooker?

A: Make sure to evenly distribute the onions in the slow cooker and avoid opening the lid frequently, as this can cause heat loss and uneven cooking. If your slow cooker tends to run hot, you may need to stir the onions occasionally.

Q: What type of bread works best for the croutons?

A: A sturdy, crusty bread like a French baguette or sourdough works best for croutons. These types of bread hold up well in the soup and provide a satisfying crunch.

Q: Can I freeze French onion soup?

A: Yes, French onion soup freezes well. Let the soup cool completely, then store it in an airtight container in the freezer for up to three months. When ready to serve, thaw and reheat the soup, then add the bread and cheese topping.

Q: Why do you add sugar to the onions?

A: The sugar helps to speed up the caramelization process of the onions, enhancing their natural sweetness and deepening the flavor of the soup.


French onion soup made in a slow cooker is a convenient and delicious way to enjoy this classic dish without the hassle of constant stirring and monitoring. With its rich, caramelized onions, savory broth, and cheesy topping, this soup is perfect for cozy evenings and special occasions alike. By following these simple steps and tips, you can create a restaurant-quality French onion soup right in your own kitchen. Whether you’re a seasoned cook or a beginner, this recipe is sure to impress and satisfy. Enjoy the comfort and flavor of homemade French onion soup, and savor the ease and convenience of using a slow cooker. Bon appétit!