This hearty and delicious slow cooker French onion soup is a classic, comforting dish. The onions are caramelized beautifully, and give the soup a really unique flavor.
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French onion soup is a family favorite all over the world. Preparing it in your slow cooker will give the onions a chance to really enhance their flavor, with little to no effort required.
If you love this recipe, you might also want to check out my Slow Cooker Leek and Potato Soup!
🥘 Ingredients
French onion soup requires a lot of fresh onions, butter, bay leaves, vegetable or beef stock as well as salt and pepper.
The French onion soup is a beautiful classic soup where the flavors of the vegetable stock and caramelized onions are in focus. Other ingredients are not typically used.
🔪 Instructions
Peel the onions and slice them thinly. Add them to the slow cooker along with the butter. Place the lid on top, and leave the slow cooker on low for 10-12 hours, or overnight. The onions will caramelize and soften.
Then, add the stock and bay leaves. Leave the soup to cook for another 7-10 hours.
Remove the bay leaves and add salt and pepper to taste.
Add the soup to oven proof bowls. Place a thin slice of bread or a baguette on top, of the soup, and add cheese. Broil the soup in an oven until the cheese has melted. Serve immediately.
🧅 Onions
French onion soup is typically made with regular yellow or brown onions, however you can also use red onions or a combination of different types of onion.
I highly recommend slicing the onions thinly and not chopping them. This will give them a nicer texture when you serve it.
💭 Top tips
My top advice for how to make the BEST french onion soup:
- The longer the onions cook, the better they are. This is definitely a recipe you don't want to rush.
- French onion soup is typically enjoyed as a broth style soup with whole slices of caramelized onions. If you're not too keen on the consistency of soft onions in soup, you can simply use a hand blender to puree the soup smooth.
🥗 Serving suggestions
Serve french onion soup with your typical soup side dishes. Extra cheesy bread or baguette is a great option. You can also serve this soup as a light appetizer.
🍲 Leftovers
Leftover slow cooker french onion soup can be stored in the fridge for up to 3 days, or frozen for up to 6 months. This recipe is perfect as a freezer meal for future dinners.
If you have leftovers, I highly recommend storing the soup without the cheesy bread on top. Otherwise, the bread will get soggy and might dissolve into the soup.
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📋 Frequently asked questions
Do I have to add any liquid to the onions? - No. The onions will release moisture as they slow cook, and no liquid is required during the caramelization process.
Is this recipe allergy friendly? - Always consult the nutrition label of the ingredients you use. This recipe is generally egg free, nut free, gluten free and soy free.
Do you need to add seasoning to onion soup? - This soup has so much flavor from the caramelized onions. Some recipes use herbs or spices like thyme and cumin, but this is strictly not necessary. If you wish, you can experiement with adding additional seasoning.
Can I make French onion soup without the bread? - Of course! If you don't want to use cheesy bread, you can serve the soup immediately straight from the Crockpot.
Which cheese should you use in French onion soup? - Gruyere is the traditional choice, but you can really use any cheese that you like.
Recipe
Slow Cooker French Onion Soup
Equipment
Ingredients
- 1 kg onions
- 2 tbsp butter
- 1 l vegetable stock (or beef stock)
- 2 bay leaves
- salt
- pepper
Instructions
- Peel the onions and slice them thinly. Add them to the slow cooker along with the butter. Place the lid on top, and leave the slow cooker on low for 10-12 hours, or overnight. The onions will caramelize and soften.
- Then, add the stock and bay leaves. Leave the soup to cook for another 7-10 hours.
- Remove the bay leaves and add salt and pepper to taste.
- Add the soup to oven safe bowls. Place a thin slice of bread or a baguette on top, of the soup, and add cheese. Broil the soup in an oven until the cheese has melted. Serve immediately.
Notes
Leftovers
Leftover slow cooker french onion soup can be stored in the fridge for up to 3 days, or frozen for up to 6 months. This recipe is perfect as a freezer meal for future dinners. If you have leftovers, I highly recommend storing the soup without the cheesy bread on top. Otherwise, the bread will get soggy and might dissolve into the soup.Top tips
My top advice for how to make the BEST french onion soup:- The longer the onions cook, the better they are. This is definitely a recipe you don’t want to rush.
- French onion soup is typically enjoyed as a broth style soup with whole slices of caramelized onions. If you’re not too keen on the consistency of soft onions in soup, you can simply use a hand blender to puree the soup smooth.
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