How to Make French Onion Soup in the Slow Cooker
French Onion Soup is one of the most popular soup recipes for a reason. It’s delicious, but takes a long time to make. This slow cooker recipe removes the hard part: keeping an eye on and stirring all day long. Use your slow cooker to make the most delicious and easy French Onion Soup, you’ll be hooked!
Make Ahead Instructions
This is the perfect make-ahead recipe. It literally takes a whole day to make it.
So you can set it the night before, go to bed, continue making it during the day, and serve it for dinner! It’s the perfect recipe for having friends over and not having to be stuck in the kitchen.
Variations:
- For a more flavorful soup, you can use a mixture of onions. This will elevate the flavor and texture of the soup. Use sweet Vidalia onion, yellow onion, and white onion.
- Don’t like Gruyere cheese? Use your favorite melty cheese like Swiss, cheddar, mozzarella, or Monterey Jack.
- Make it gluten-free by using your favorite gluten-free bread.
- Want to make it vegetarian? Use vegetable broth instead of beef broth
- Add fresh herbs like thyme and sage for a different flavor profile.
Store French Onion Soup
Let the soup cool down to room temperature, place it in an airtight container, and store it in the fridge for up to 4 days.
When ready to serve, heat in the microwave or stove top, ladle onto a bowl, top with bread and cheese, bake, and broil until melted and toasty.
Freeze French Onion Soup
This soup can be frozen without the bread and cheese. Place the cooled-down soup in an airtight container or freezer bag, and freeze for up to 3 months.
When ready to serve, thaw overnight in the fridge, reheat in the microwave or stove top, ladle into a bowl, top with bread and cheese, bake, and broil.
How to Make French Onion Soup in the Slow Cooker
Ingredients
- 3 lbs yellow onions, peeled, quartered, and sliced
- 2 tbsp unsalted butter
- 2 tbsp olive oil
- 1 tsp salt, or to taste
- Freshly cracked black pepper to taste
- 2 bay leaves
- 2 sprigs of fresh thyme
- 10 cups low-sodium beef broth
- 2 tbsp balsamic or sherry vinegar
- 8 slices crusty bread
- 2 cups Gruyere cheese, freshly shredded
Instructions
- Place the sliced onions in the pot of your slow cooker. Season with salt and pepper. Add the butter and olive oil. Place the lid on and cook on low for 12 hours or overnight until the onions are dark brown and caramelized.
- Stir in the beef broth, vinegar, thyme, and bay leaves, and cook on low for an additional 6 hours.
- Divide the soup into 8 bowls, top with a slice of toasted crusty bread, and divide the shredded cheese evenly on top of the bread.
- Bake for 20 minutes and broil for 2 until the melted cheese is slightly golden.
Nutrition
FAQ About Slow Cooker French Onion Soup
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1. Do I Really Need to Caramelize the Onions Before Using the Slow Cooker? No, you don’t! Letting them slow cook with olive oil and butter for 12 hours will yield the same result as caramelizing them in a skillet.
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2. Can I Swap Gruyere with Another Cheese? Yes, you can. Although Gruyere is the classic cheese used to make French Onion Soup, you can use your favorite melty cheese like Swiss, mozzarella, Parmesan, or Cheddar.
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3. How can I Make the Soup a Bit Less Salty? Use low-sodium beef broth and this will take care of the problem! You can always place the salt on the table and let people add as much as they want.
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4. How Do I Prevent the Bread From Getting Soggy? Toasting the bread before placing it over the soup and baking it will prevent it from getting too soggy. It will soften a bit, but a lot less. Toasting it creates a crunchy base that won’t soak up as much liquid.
