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Ingredients for crock pot French onion soup.

Slow Cooker French Onion Soup

  • Author: RebeccaBlackwell
  • Yield: 4 bowls of soup


Traditionally, French onion soup is made by cooking onions for a long time on the stove top over low heat until they are rich golden brown. This makes a delicious, flavorful broth, but it's also time consuming and requires you to be home for the several hours that the onions are cooking. Cooking the onions all day in a slow cooker is SO much easier and still produces a delicious, flavorful French onion soup.


  • 8 lbs yellow onions (see recipe note)
  • 5 tbsp butter, cut into 5 pieces
  • 1 1/2 tsp all-purpose flour
  • 4 cups chicken broth (see note)
  • 4 cups beef broth
  • 1/2 cup dry white wine
  • 2 tsp dried thyme
  • 1 bay leaf
  • Salt and pepper, or to taste
  • 8 oz grated gruyere cheese
  • About 1 cup of Croutons (see note)


  1. Peel the onions and cut them into quarters. Using a sharp knife, cut each quarter into slices, approximately 1/4 inch wide. Alternatively, use the 4 MM slicing blade of your food processor to cut the onion quarters into slices.
  2. Pile the sliced onions into a slow cooker.  The pot will be quite full of onions. Use your hands to press them down if the pot is over flowing. Scatter the pieces of butter over the top of the onions and sprinkle with about 1 tsp salt. Cover, and cook on high for 10 hours, at which point the onions should be a rich golden color.
  3. Dump the onions into a large heavy bottom sauce pan or dutch oven. (If you are planning to use some of the onions later in the week for Pot Roast Sandwiches and Creamy Chicken and Rice, remove 1 1/2 cups of the onions and store in an airtight container in the refrigerator.)
  4. Sprinkle the flour over the top of the onions and cook over medium-high heat for 2-3 minutes, stirring constantly. Stir in the chicken and beef broth, wine, thyme, bay leaf, and about 1 tsp each salt and pepper. Bring to a boil and allow to simmer uncovered, stirring occasionally, for 30-45 minutes, until the liquid has reduced by about a third and the broth has thickened slightly. Taste, and add more salt and pepper if desired.
  5. Preheat the broiler.
  6. Remove the pan from the heat and ladle the hot soup into 4 soup bowls, filling each to within about 1-inch of the top. Place the soup bowls on a baking sheet. Top each with several croutons - enough to cover the surface of the soup. Distribute the grated cheese amongst the 4 bowls, covering the croutons.
  7. Slide the baking sheet with the soup bowls into the oven under the broiler and cook for a couple of minutes, until the cheese is melted, bubbling, and just beginning to brown. *Watch carefully. The cheese will go from brown to burnt in an instant.
  8. Carefully remove from the oven. Use oven mitts to place each soup bowl on a plate and serve


  • This recipe uses 8 pounds of onions, which is actually more than you need if you're only making French onion soup. If you're making this soup as a part of Weekly Winter Meal Plan #2, the extra onions will be used later in the week to make Open Face Pot Roast Sandwiches and Creamy Chicken and Rice. If you're not making this soup as a part of that weekly meal plan, you'll only need about 6 pounds of onions.
  • Gruyere cheese is incredibly delicious melted over French onion soup. It's also quite expensive. If you'd rather use a different cheese, Swiss, Asiago, Mozzarella, or Pecorino Romano also work well. Or any combination of the above.
  • Category: Soups and Stews