Rich, delicious tasting French Onion Soup in the Slow Cooker uses beef bones for a meaty base and delivers true French Onion Soup flavor in your crockpot.
This is the second recipe for French Onion Soup I’ve posted for you. I have another French Onion Soup recipe that is made in your oven and is true to form French Onion Soup. But I’ve also been wanting to make French Onion Soup in the slow cooker. I was challenged to make sure this version didn’t become a watery, soggy onion broth with washed out flavor. So I set to work and the results could not have been more rewarding.
French Onion Soup in the slow cooker calls for a bit of prep work, but it’s well worth the effort. I even have a foolproof no-tears way to slice up those 6 onions you’ll need for the recipe.
Starting with some standard French Onion Soup ingredients, we have several onions, beef and chicken broth plus dry sherry or white wine (non-alcoholic cooking varieties work perfectly fine). But to boost the depth of flavor, we’re going to experiment by adding apple butter, soy sauce and 2 pounds of beef bones.
Let’s get started with slicing up all those onions. Why do we cry when cutting into an onion? Well, here’s a tiny bit of science about that. When you cut into an onion, you break cells in the onion that release gases that waft up into your eyes and when mixed with the tears in your eyes, these gases produce sulfuric acid. This interaction stimulates your eyes to release more tears to wash away the irritant. If you are a contact lens wearer, you won’t have the tearing up problem since your lenses prevent the gases from getting into your eyes. If you don’t have contacts to protect you, I have a guaranteed, easy solution for you. Just don a pair of swim goggles before diving into your bunch of onions, forgive the pun. (You can actually buy Onion Goggles, but really, why?) Presto, no-tears onion slicing. Put your onions in the slow cooker and drizzle melted butter and salt and pepper over them.
Next, let’s get those bones and other aromatic flavors into the mix. Beef bones are going to make your French Onion Soup rich and super flavorful. The bones can be found in most freezer meat sections in your local supermarket, or ask for some from behind the meat counter. The bones need to be cooked through in your microwave before being added to the slow cooker.
Once the beef bones are browned, you’re going to whisk apple butter, soy sauce, sherry or wine, thyme and a tiny bit of brown sugar together. Now, pour this mixture over the onions, nestle the beef bones in and cover to slow cook for about 8 hours.
Eight hours later and your kitchen smells mouth-watering amazing. Remove and discard the bones, and pour in heated chicken broth and beef broth. While the soup is warming in the slow cooker, toast some baguette slices and melt Gruyère and/or mozzarella cheese on the toast. The cheese baguette slices will soak up some of the broth for the ultimate French Onion Soup experience. Easy from your own kitchen, special for your own family.
This version is just a touch sweeter than my oven version, and even though my other recipe is titled the “best” French Onion Soup recipe, this one is the best you will make in your slow cooker or Crockpot.
French Onion Soup in your Slow Cooker
- 2 pounds beef bones
- 6 yellow onions, halved and sliced 1/4 inch thick (Do NOT use sweet onions)
- 4 Tablespoons 1/2 stick butter, melted
- 1 teaspoon salt
- 1 teaspoon pepper
- 1 teaspoon brown sugar
- ¼ teaspoon dried thyme or 1 teaspoon minced fresh thyme
- 2 ½ Tablespoons cornstarch
- ⅔ cup apple butter. Do not add more than this or your soup may be too sweet
- ¾ cup dry sherry or white wine, non-alcoholic cooking version works fine
- ¼ cup soy sauce
- 32 oz. low-sodium chicken broth
- 32 oz. beef broth
- 1 loaf French baguette, cut into 1/2-inch slices
- 2 ½ cups shredded Gruyere cheese or mozzarella
- Slice onions and place into slow cooker. Drizzle butter, 1 teaspoon salt and 1 teaspoon pepper, brown sugar and thyme over onions and toss.
- Arrange beef bones on paper towel-lined plate and microwave until well browned, about 8 minutes.
- Whisk cornstarch, apple butter, sherry and soy sauce together in bowl until smooth, then stir into slow cooker. Nestle microwaved bones into onions. Cover and cook on high setting until onions are softened and deep golden brown, about 8 hours.
- Discard beef bones. Bring chicken broth and beef broth to boil in covered saucepan over high heat, then stir into slow cooker. Add more salt and pepper to taste, if needed. Let soup sit until heated through and while you prepare the baguettes.
- Just before serving, position oven rack 6 inches from broiler element and heat broiler. Lay bread on baking sheet and broil until golden on both sides. Sprinkle cheese over one side of bread and continue to broil until melted and bubbly. Ladle soup into serving bowls and top with broiled cheese bread.
Revised from The Slow Cooker Revolution.