This low-carb version of French onion soup is cheesy and flavorful. Make this bread-free soup in your slow cooker or electric pressure cooker (Instant Pot).
Updated 2019 With Video
It’s almost the new year which means the start of new years diets for most people. It’s no secret that low-carb / keto lifestyles are all the rage right now. Heck, I even wrote a low-carb cookbook, The Healthy Low-Carb Slow Cooker Cookbook (shameless plug). Since French onion soup is my favorite soup, I decided to make a low-carb/keto version and I’m so glad I did; this soup was an instant hit in my house. I know traditionally French onion soup is served with bread underneath the melted cheese. I had to omit the bread to make it low-carb (yes, you can use a low-carb bread but I have not tried it). What I learned from creating this recipe is that I don’t need bread to love French onion soup. Yes, bread adds a certain je ne sais quoi but I still think the flavors that we all love so much are still there in this soup without it.
Traditional French onion soup uses caramelized onions. This recipe is written using non-caramelized onions. The onions go in raw and they cook until they’re extremely soft but not necessarily caramelized. It’s not the traditional way but it’s a lot faster and personally I think the soup is great without it. What type of onions should you use? I used white onions. You can use your preferred onion whether it be white, sweet, yellow, or even red.
Using Caramelized Onions
If you’re one of those people who thinks that French onion soup has to be made with caramelized onions, the good news is that this can easily be made in the slow cooker or electric pressure cooker (Instant Pot). No more standing over a stove stirring onions, you sit back let the appliance do the work. When the onions are caramelized to your liking, simply add the rest of the ingredients for the French onions soup. For the slow cooker, this will be a long process. It takes 10-12 hours to caramelize onions in the slow cooker so if you’re going to use the slow cooker, I suggest you start the night before, caramelize the onions overnight, and in the morning add the rest of the ingredients to start the soup. Using the electric pressure cooker, it’s done a heck of a lot faster. The video below shows how to make this soup using caramelized onions.
What I love most about French onion soup is the mounds of melted cheese on top. That’s what it’s all about even though the majority of the time, this recipe cooks without it. What kind of cheese should you use? If I’m feeling fancy, I’ll use shredded Gruyère cheese. Most days though, I just add 1 or two slices of swiss cheese. Sliced or shredded cheese, it doesn’t matter.
How much cheese to use?
I list two cups for the recipe but if you really like cheese, add more cheese. Want less? Use less. If I’m using shredded cheese, I usually add approximately 1/3 cup of shredded cheese on top of each ramekin; if I’m using sliced cheese, I usually add 2 slices per ramekin. Keep in mind that since this is a low-carb version and there’s no bread to put the cheese on top of, the cheese will sink down slightly into the ramekin. This may cause it to look like you don’t have as much cheese in your soup than you actually do. Not that there’s anything wrong with lots of cheese.
Broil the soup until the cheese is nice & bubbling and starting to brown. I suggest you monitor the soup as is broils to ensure the cheese doesn’t burn. This soup is best served warm while the cheese is stringy.
I used a 3.5-quart slow cooker for this recipe but you can easily doubled the recipe and use a 5 or 6-quart if you’re feeding a larger crowd.
- 2 large white onions, sliced thin (approximately 2 pounds)
- 6 cups low-sodium beef or your preferred broth
- 2 cups cheese (or more)
- 1 tablespoon butter or oil
- 1 garlic clove, minced
- 1 teaspoon salt
- 1/2 teaspoon dried thyme
- 1/4 teaspoon pepper
- 1 bay leaf
- Add all the ingredients EXCEPT the cheese to the slow cooker. Stir to mix well.
- Cook HIGH 3-4 hours, LOW 6-8. Remove bay leaf.
See FINAL STEP below
- Set Instant Pot to the high saute setting. Once hot, add butter/oil. Add onion and cook, stirring occasionally, until tender, about 3-5 minutes. Add garlic and cook an additional minute. Turn off pressure cooker.
- Pour in broth and deglaze the bottom of the pressure cooker by scraping all the bits off with a wooden spoon. Stir in salt, pepper and thyme. Add bay leaf.
- Close lid and seal valve. Set high pressure and cook for 25 minutes, natural release. Remove bay leaf.
See FINAL STEP below
FINAL STEP (you will need ovenproof bowls)
Preheat broiler. Ladle the soup evenly into bowls & each bowl evenly with cheese. Arrange bowls on a large baking sheet. Place baking sheet carefully under the boiler and broil a few minutes or until cheese is melted and starting to brown slightly.
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