Slow Cooker French Onion Soup
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Did you know you can make French onion soup in the crockpot?! It’s ridiculously easy with basically no stirring and no work!
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Reasons to make slow cooker french onion soup
- So easy. This French onion soup is ridiculously easy to whip up with so much hands-off cooking thanks to the crockpot.
- No babysitting caramelized onions. No one, and I really do mean no one, is babysitting the caramelized onions here. Nope. We’re throwing them all in the crockpot and letting it do all the heavy lifting for us.
- Cozy, hug-in-a-bowl vibes. This soup is oh-so-perfect for a chilly, blustery snow day, keeping you warm and cozy all day long from the inside out.
- Freezer-friendly. French onion soup is a great recipe to freeze for later, allowing for easy thawing and reheating for those super busy weeknights.
what is french onion soup
French onion soup originated in France in the 18th century – a common staple as onions were plentiful, cheap and easy to grow. It is a soup of caramelized onions typically cooked in beef stock, topped with bread and cheese.
tips and tricks for success
- Use sweet onions. Although most recipes call for yellow onions, sweet onions allow for deeper caramelization, resulting in a more rich, pleasant sweetness to the soup.
- Use good-quality stock. The better quality your stock, the better your soup. Many brands love to pack in the salt so always opt for unsalted or a lower-sodium variety.
- Gruyere cheese is key. Gruyere is traditionally used in French onion soup for its rich, nutty flavors and great melting capabilities.
- Use oven-safe bowls. Ramekins, great for individual servings, can withstand high heat under a broiler.
- Freeze as needed. French onion soup is very freezer friendly. Freeze without the baguette slices and cheeses, and store up to 3 months.
what to serve with french onion soup
Slow Cooker French Onion Soup: Frequently Asked Questions
Absolutely! But because dried herbs are often more potent/concentrated than fresh herbs, you need less when using dry. The correct ratio is 1 tablespoon fresh herbs to 1 teaspoon dried herbs.
You can substitute the sherry vinegar with white wine, dry vermouth, apple cider vinegar or rice wine vinegar.
Swiss cheese or fontina cheese are suitable alternatives.
We highly recommend a baguette or other crusty French bread.
No crockpot, no problem! We have a stovetop recipe here.
Leftovers can be stored in an airtight container in the fridge for 3-4 days, storing separately from the baguette slices and cheese.
Absolutely! Let cool completely; portion into plastic freezer bags in individual servings, squeezing out any excess air before sealing. Lay the bags flat in a single layer in the freezer (this will help them freeze quickly). To reheat, thaw overnight in the fridge, reheating over low heat, stirring occasionally, until heated through. When ready to serve, add your baguette slices and cheeses!
Slow Cooker French Onion Soup
Ingredients
- 3 pounds sweet onions, thinly sliced
- 3 tablespoons unsalted butter, melted
- 2 teaspoons brown sugar
- Kosher salt and freshly ground black pepper, to taste
- 6 sprigs fresh thyme
- 1 bay leaf
- 6 cups beef stock
- 2 teaspoons sherry vinegar
- 1 French baguette, sliced
- 1 cup shredded gruyère cheese
- 1 cup shredded asiago cheese
Equipment
Instructions
- Place onions into a 6-qt slow cooker.
- Stir in butter, brown sugar and 1 teaspoon salt; top with thyme and bay leaf. Cover and cook on high heat for 8-10 hours, or until onions are caramelized and browned.*
- Stir in beef stock and sherry; season with salt and pepper, to taste. Cover and cook on high heat for 2-3 hours, or until heated through. Remove and discard thyme and bay leaf.
- Preheat oven to broil.
- Place baguette slices onto a baking sheet. Place into oven and broil until golden brown on both sides, about 1-2 minutes per side; set aside.
- Divide soup into ramekins or ovenproof bowls. Place onto a baking sheet. Top with baguette slices to cover the surface of the soup completely; sprinkle with cheeses.
- Place into oven and broil until golden brown and cheeses have melted; about 2 minutes.
- Serve immediately.
Video
Notes
Did you make this recipe?
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Can you freeze leftovers?
Delicious! Made this last night for dinner and it was SO good! I caramelized the onions with butter, bay leaf, thyme and salt in the Instapot on sauté – then I finished it in my instapot on slow cooker mode on low for maybe 5 hours, finished as directed in oven. I used a mandolin to slice the onions, made it nice and quick – Best French Onion Soup we’ve ever had!
LOL – 10 hrs of cooking before prepping. So we are starting at around 7 am in order to be done for dinner – ok. Let’s get cracking !!!
Is there an instant pot version vs slow cooker ?
Fantastic soup! I exactly followed the directions and was so impressed with the delicious taste and ease of making it.
So, for some crockpots, high is too much for 8-10 hours. I had crispy and burnt onions around the sides of mine after 3 hours. Some damage control and dropping to low resulted in beautiful dark onions after 8 hours. The rest of the recipe is quite good.
Do we cut up the onions or just put the whole onions in the pot?
This was phenomenal! I caramelized my onions in a pot with the butter and brown sugar then put my beef broth and sherry vinegar and brought is all to a boil then transferred it to a hot crock pot. Cooked for about 4 hours and it was delicious! As for the cheese I broiled it on parchment paper until golden and laid it over the top.
#damndelicious
Can vegetable broth be used?
Would the flavor change much? Thank You.
Hi there, I used veggie broth since my daughter is vegetarian and we loved it.
An excellent french onion soup. Very easy to make and trouble free. Followed directions as written and worked out perfect. The rest of the readers should do the same and stop questioning you. Thanks so much for posting, its a keeper for sure
My favorite cozy fall meal.
This is a go-to recipe. Absolutely love it. I’ve also used the first part of the recipe, caramelizing the onions, and then put them in small baggies to freeze for ease when I need caramelized onions. Perfect. Thank you!
i HAVE MADE THIS TWICE AND THE SECOND TIME WAS EVEN BETTER. LOVE HOW EASY. GREAT WAY TO USE UP THOSE EXTRA ONIONS. USED FRESH ROSEMARY FROM THE GARDEN AND IT WAS DELICIOUS.
This is a HUGE hit in my house. I’ve made it several times and I get compliments. Vidalia onions work very well. But I’ve used yellow and white onions with tremendous success. Also, be sure to use fresh thyme as it makes a big difference.
Thank you for another great recipe.
DELICIOUS!! Love this recipe!
Can sherry cooking wine be subbed for the sherry vinegar?
Thanks!
Evidently you can combine red vinegar with sherry: 3:1 ratio and get a good substitute.
wondering about onions in soup that will be frozen as I’m cooking for one. Will the onions go bad faster when frozen and thawed, then other vegetables and legumes.?
Ohmigosh! Best soup ever! The sherry vinegar makes all the difference. Don’t substitute. Gave some to 3 friends and they confirmed it was awesome! Thank u for the fabulous recipe.
Many thanks Chungah ….Enjoyed this easy recipe and yes, as asked by one of your fans, I made it in a multicooker on the slow cooker setting. I do not own a crock pot/slow cooker and it worked out really well. As with any type of cooking, keep an eye on your pot and adjust time if necessar. The recipe took a considerably shorter time to cook. I started off on high and changed to low setting. I did not have any dried or fresh herb seasonings other than some italian seasoning so that is what I used. I try not to stress when adapting a recipe..whats the worst that can happen? I also added 3 cloves of garlic…love that stuff and used sliced swiss cheese because that’s what was in the fridge. That is half the fun, experimentation! Again many thanks for giving me ideas for variations Chungah.
Has anyone made this with an InstaPot-like multiicooker? The reason I ask, with most Crock-Pot type cookers their heating elements are around the sides … where the heating elements of multi-cookers are on bottom. Just concerned about burning because of this difference.