Slow Cooker French Onion Soup
French Onion Soup made easy in the slow cooker. Caramelized onions in a rich broth, topped with toasted baguette and melty gruyère cheese.
Hot, cheesy French Onion Soup made easy in the slow cooker. This soup is full of soft, melty caramelized onions in a rich broth and gratinéed with toasted baguette croutons and bubbly gruyère cheese. It’s a warming, comforting bowl of delicious French onion flavour.
Why you’ll love this French onion soup recipe
- It’s easy to make. Aside from slicing onions and shredding cheese, there’s very little hands-on work required. The slow cooker does all the heavy lifting, including caramelizing the onions!
- Only 10 ingredients. Most of which you likely already have in your fridge or pantry. If not, see the recipe card for optional substitutions.
- It’s vegetarian-friendly. This recipe uses mushroom broth instead of beef broth to deliver a rich, umami plant-based soup that doesn’t compromise on flavour.
How to make French onion soup in the slow cooker
Step 1: Caramelize the onions. In a slow cooker pot, add the onions, butter, brown sugar, tamari, thyme, pepper, and salt. Cover and set to slow cook on “Low” for 8-10 hours to caramelize the onions.
Step 2: Add the broth. After the onions have cooked down and caramelized, add the broth and stir well, scraping up any browned bits from the bottom of the pot. Cook for 5 minutes, until the broth is heated through.
Step 3: Toast the baguette. Meanwhile, toast 4 baguette slices until golden brown and crispy, like a crouton. If desired, brush each slice with olive oil and season with salt and pepper before toasting.
Step 4: Assemble. Place 4 oven-safe lion head soup bowls or ramekins on a baking sheet. Ladle the soup into the bowls. Top each bowl with a baguette crouton and a handful of shredded cheese.
Step 5: Broil. Broil in the oven until the cheese is melted, bubbly, and beginning to brown, about 3 minutes. Bon appétit!
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Also, don’t miss my Slow Cooker Tortellini Soup with fresh tortellini in a light, but rich tomato broth seasoned with Italian herbs and red pepper flakes. It’s hearty and warming, the perfect remedy for cold, snowy days!
Slow Cooker French Onion Soup
Ingredients
- 4 yellow onions, thinly sliced
- ¼ cup butter
- 1 tablespoon brown sugar
- 1 tablespoon tamari
- ½ teaspoon dried thyme
- ½ teaspoon cracked black pepper
- ½ teaspoon salt
- 6 cups mushroom broth
- ½ baguette, sliced
- 1 cup gruyère cheese, shredded
Instructions
- In a slow cooker pot, add the onions, butter, brown sugar, tamari, thyme, pepper, and salt. Cover and set to slow cook on “Low” for 8-10 hours to caramelize the onions.
- After the onions have cooked down and caramelized, add the broth and stir well, scraping up any browned bits from the bottom of the pot. Cook for 5 minutes, until the broth is heated through.
- Meanwhile, toast 4 baguette slices until golden brown and crispy, like a crouton. If desired, brush each slice with olive oil and season with salt and pepper before toasting.
- Place 4 oven-safe lion head soup bowls or ramekins on a baking sheet. Ladle the soup into the bowls. Top each bowl with a baguette crouton and a handful of shredded cheese.
- Broil in the oven until the cheese is melted, bubbly, and beginning to brown, about 3 minutes.
Notes
- Onions: You can also use white or red onions.
- Broth: French onion soup is traditionally made with beef broth, however I like to use mushroom broth to keep this soup vegetarian-friendly. Feel free to use whichever broth you prefer best: beef, chicken, mushroom, or vegetable.
- Bread: You can also use cubed or sliced crusty day-old bread.
- Cheese: You could also use Comté, Swiss, provolone, or fontina cheese in place of gruyère.
