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Slow Cooker French Onion Soup

This Slow Cooker French Onion Soup is incredibly easy and so rich and full of flavor. See why this comforting soup is always a family favorite!

A CLASSIC SOUP MADE IN THE CROCK POT

Are you looking for an incredibly flavorful and comforting soup that is easy to make? With very minimal prep work required, this tasty soup can be put together in the morning and left to its own devices all day and be ready-to-enjoy meal at dinnertime. Rich beef broth combines with caramelized onions, herbs, and cheese served atop each bowl of creamy goodness to create an unbeatable taste sensation! So comforting and good, I could literally eat this every day. Cooking for so long in the crock pot really condenses the flavor!

A spoon holding a bite of French Onion Soup.

FREQUENTLY ASKED QUESTIONS:

Why use a Slow Cooker for French Onion Soup?

I know it may seem a little crazy to use the slow cooker when you have to transfer it to a bowl to add the bread and melt the cheese and on top and use a skillet to caramelize the onions. But, trust me, the soup is so flavorful after 9 hours in the slow cooker. Cooking it low and slow really lets the flavors develop and gives it a richness that you wouldn’t get from a stovetop soup, unless it was on the stovetop for hours and nobody has time to man the stove that long.
You can see if your slow cooker has a sauté option which may help eliminate the need to sauté the onions on the stove first.

What makes French onion soup French?

French Onion Soup is French because its origins can be traced back to 18th century France. It typically consists of beef broth, caramelized onions, and either stale bread or croutons topped with melted cheese. Traditional recipes also often include brandy, garlic, thyme, bay leaves and other spices. This savory soup is a popular dish around the world and has been adapted to many different cultures’ tastes.

What is the difference between onion soup and French onion soup?

The main difference between onion soup and French onion soup is that the French version is usually made with beef broth or stock, while regular onion soup can be made with either beef or chicken broth. Additionally, French onion soups are typically served with a crust of bread and melted cheese on top while regular onion soups often don’t traditionally use those toppings.

What wine is best for French Onion Soup?

A dry white wine, such as a Sauvignon Blanc or Pinot Grigio, is the best choice for French Onion Soup. The acidity of the wine helps to balance out the sweetness from the onions and compliments the savory flavors in the soup. In addition, white wine won’t overwhelm or change the flavor of your soup like red wines can. If you prefer to use a red wine, then go with a light-bodied variety like Pinot Noir. We used cooking sherry as that’s a common ingredient in an American French Onion soup.

How can I thicken French Onion soup?

If you like it really thick, the best way to do that is by stirring in a mixture of cornstarch and cold water (it’s called a slurry.) In a small bowl, mix together 1 Tablespoon of cornstarch with 1 Tablespoon of cold water until combined. Then, add this mixture to the soup and stir until it thickens. You can also add small pieces of butter or cream for additional thickness if desired.

What other cheese can I use?

Instead of shredded Gruyere, you can use sliced. I recommend at least 2 slices per serving. If you rather not use Gruyere, try Swiss or provolone in its place.

What kind of bowl do I need to use?

Once the soup has cooked in the slow cooker, you can transfer it to a broiler safe, oven safe bowl or small skillet. If it’s not rated as safe for broiler use, it may crack or damage the bowl when you go to melt the cheese.
If you don’t have a safe bowl, just melt the cheese directly on the sliced baguettes in the oven then put them on top of the individual serving bowls. 

Do I have to use cooking sherry?

I think it really adds depth to this soup. But, if you want to swap it out, try apple cider vinegar. It will give it just enough tang to really give that dynamic flavor without making it taste like a separate ingredient. Or you can just omit the ingredient altogether.

How to store leftovers?

Leftover soup can be stored in an airtight container in the fridge for up to 5 days.

Can you freeze French onion soup?

Yes! You can freeze this delish soup for up to 3 months in a freezer safe container.

A white skillet of homemade French Onion Soup with melted cheese on top.

INGREDIENTS NEEDED: (SEE RECIPE CARD BELOW FOR THE FULL RECIPE)

  • salted butter
  • sweet onions
  • black pepper
  • garlic
  • cooking sherry
  • beef stock
  • Worcestershire sauce
  • fresh thyme
  • bay leaf
  • French baguette
  • olive oil
  • gruyere cheese
Salted butter, sweet onions, black pepper, garlic, cooking sherry, beef stock, Worcestershire sauce, thyme, bay leaves, French baguette, olive oil, and gruyere cheese.

HOW TO MAKE SLOW COOKER FRENCH ONION SOUP:

In a large skillet over medium heat, melt the butter. Add the onions and pepper to the skillet and coat them with the butter. 

sliced onions and black pepper shown in a large skillet.

Continue to cook, occasionally stirring, until caramelized and browned, 45-60 minutes. During the last 20 or so minutes, the onions will have a tendency to burn if you do not stir them often enough, so make sure to keep them moving and keep an eye on them. Add the garlic and cook until fragrant, 30 seconds.

Cooked onions in a pan with garlic on top.

Deglaze the pan with the cooking sherry and take off the heat. 

A measuring cup pouring liquid in a pan to deglaze it.

Add the onions to a 6-8 quart slow cooker. 

Cooked onions and garlic in a crock pot insert.

Add the beef stock, Worcestershire sauce, thyme, and bay leaf to the cooker. Stir to combine and place on high for 3-4 hours or low 6-8 hours. After cooking, remove the sprigs of thyme and the bay leaf. 

A slow cooker with onions, beef stock, Worcestershire sauce, thyme, and bay leaf.

When you are ready to serve, preheat the oven to 425°F. Lay the baguette slices on a large sheet tray and brush both sides with the olive oil, it seems like a lot, but use it all.

Sheet pan with sliced baguettes being brushed with topping.

Bake for 5-6 minutes per side, flipping once until lightly golden and toasted.

Baked French Baguettes.

Place the soup into a broiler-safe crock or bowl, leaving about ½ inch at the top of the bowl.

Skillet of French Onion Soup made in the Slow Cooker.

Place a few of the toasted bread slices on top, and top generously with the shredded cheese, try to cover up the toast as much as possible. Put the bowls on a sheet tray to catch any drips.

Skillet bowl of French Onion Soup with baguettes and cheese on top waiting to bet under the broiler.

Place the bowls under the broiler until dark golden brown, let cool because it is extremely hot, and serve.

Looking down on a serving of French Onion soup made in the Slow Cooker.

CRAVING MORE RECIPES?

A skillet filled with Slow Cooker French Onion Soup.

Slow Cooker French Onion Soup

This Slow Cooker French Onion Soup is filling, rich and delicious- all made in the Crockpot.
5 from 5 votes
Print Pin Rate
Prep Time: 15 minutes
Cook Time: 9 hours
Total Time: 9 hours 15 minutes
Servings: 8 servings

Ingredients

  • 4 Tablespoons salted butter
  • 5 medium sweet onions, thinly sliced (like Vidalia onions)
  • ½ teaspoon black pepper
  • 4 cloves garlic, minced
  • cup cooking sherry
  • 64 ounces beef stock
  • 1 Tablespoon Worcestershire sauce
  • 6 sprigs fresh thyme
  • 1 bay leaf

For serving:

  • 1 French baguette, cut into ½ inch slices
  • ¼ cup olive oil
  • 14 ounces gruyere cheese, shredded

Instructions

  • In a large skillet over medium heat, melt 4 Tablespoons salted butter. Add the 5 medium sweet onions, thinly sliced and 1/2 teaspoon black pepper to the skillet and coat them with the butter.
  • Continue to cook, occasionally stirring, until caramelized and browned, 45-60 minutes. During the last 20 or so minutes, the onions will have a tendency to burn if you do not stir them often enough, so make sure to keep them moving and keep an eye on them.
  • Add 4 cloves garlic, minced and cook until fragrant, 30 seconds.
  • Deglaze the pan with 1/3 cup cooking sherry and take off the heat.
  • Add the cooked onions to a 6-8 quart slow cooker.
  • Add 64 ounces beef stock, 1 Tablespoon Worcestershire sauce, 6 sprigs fresh thyme and 1 bay leaf to the slow cooker. Stir to combine and place on high for 3-4 hours or low 6-8 hours. After cooking, remove the sprigs of thyme and the bay leaf.
  • When you are ready to serve, preheat the oven to 425°F.
  • Lay the 1 French baguette, cut into ½ inch slices on a large sheet tray and brush both sides of the slices with ¼ cup olive oil, it seems like a lot, but use it all.
  • Bake for 5-6 minutes per side, flipping once until lightly golden and toasted.
  • Place the soup into a broiler-safe crock or bowl, leaving about ½ inch at the top of the bowl.
  • Place a few of the toasted bread slices on top, and top generously with 14 ounces gruyere cheese, shredded, try to cover up the toast as much as possible. Put the bowls on a sheet tray to catch any drips.
  • Place the bowls under the broiler until dark golden brown, let cool because it is extremely hot, and serve.

Notes

  • It is not too salty from using both salted butter and beef stock. But, if you are watching your salt intake, start with both unsalted stock and butter, then taste and adjust the seasoning.
  • You can use 1 teaspoon of dried thyme if you don’t have fresh.
  • You absolutely have to make sure the bowl you use to broil the cheese is rated for use under the broiler. If not, it may crack or damage the bowl. If you don’t have an oven safe bowl, you can just melt the cheese directly on the baguettes in the oven then transfer to the serving bowls. 
  • If you are not planning to eat the entire soup in one sitting, I suggest only making enough croutons/toasts for how much you are planning to eat. They may become soggy if left in an airtight container at room temperature for multiple days.
  • It seems like a lot of cheese for the recipe, you really need to add a generous portion to each bowl to get the signature “french onion soup” look.
  • Keep leftovers in the fridge for up to 5 days, freeze for up to 3 months
Course: Soup
Cuisine: French

Nutrition

Calories: 505kcal | Carbohydrates: 35g | Protein: 24g | Fat: 30g | Sodium: 1087mg | Fiber: 3g | Sugar: 14g

Nutritional Disclaimer

“The Country Cook” is not a dietician or nutritionist, and any nutritional information shared is an estimate. If calorie count and other nutritional values are important to you, we recommend running the ingredients through whichever online nutritional calculator you prefer. Calories and other nutritional values can vary quite a bit depending on which brands were used.

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Recipe Rating




3 Comments

  1. 5 stars
    I made this & it was definitely a 5* soup! Used soy sauce instead of Worcestershire & vegetable broth instead of beef. It’s definitely one I’ll be making again.

  2. Hello again Brandie! I have a severe allergy to Worcester sauce. What would you use in exchange. I thought that maybe soy sauce or tamari would work, but I don’t know if it would overrun the soup. Any other suggestions would be helpful. I have been wanting to make this soup for a long time and that is what is stopping me, honestly.