For those embracing a low-carb or ketogenic lifestyle, the new year often brings a renewed focus on dietary choices. Fortunately, enjoying classic comfort foods doesn't have to be a thing of the past. This keto French onion soup recipe delivers a cheesy, flavorful experience without the carb overload. It's a bread-free, low-carb friendly soup recipe that will impress any crowd.
The Allure of French Onion Soup
French onion soup is renowned for its rich flavor and comforting warmth. Traditionally, it begins with caramelizing onions to unlock their natural sweetness, transforming them into a deep golden hue. It is a classic French dish made low carb and blood sugar friendly.
A Keto-Friendly Adaptation
Traditional French onion soup often includes bread, which is not ideal for a keto diet. This recipe omits the bread to make it low-carb. What I learned from creating this recipe is that I don’t need bread to love French onion soup. While low-carb bread can be used, this recipe proves that bread isn't essential for enjoying this classic soup.
The Onion Question
Traditional French onion soup uses caramelized onions. This recipe is written using non-caramelized onions. For those who prefer the traditional caramelized flavor, 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. Using the electric pressure cooker, it’s done a heck of a lot faster.
As for the type of onions, white onions are a great choice. 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.
Read also: Delicious Keto Soup
Choosing the Right Cheese
What I love most about this slow cooker French onion soup recipe is the melted cheese on top. That’s what it’s all about even though the majority of the time, this recipe cooks without it. When it comes to cheese, Gruyère is a fancy and flavorful option. Most days though, I just add 1 or two slices of swiss cheese. The recipe lists two cups for the recipe but if you really like cheese, add more cheese. Want less? Use less. If you can’t get it or aren’t a fan of the flavor, a mild cheese like mozzarella or muenster will work just as well. Cheddar will definitely stand out and compete with the flavor of the soup so I’d use it as a last resort unless you are looking for that kind of effect.
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. 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.
Recipe Variations and Tips
Slow Cooker Instructions
Add all the ingredients EXCEPT the cheese to the slow cooker. Cook HIGH 3-4 hours, LOW 6-8. 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.
Instant Pot Instructions
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. 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. Close lid and seal valve.
Broiling
Preheat broiler. Ladle the soup evenly into bowls & each bowl evenly with cheese. Arrange bowls on a large baking sheet.
Read also: Easy Low-Carb Cheese Crackers
Keto French Onion Soup with Cheesy Crouton Topper
This super tasty Keto French Onion Soup is coming at you with a rich, flavorful broth, sweet strands of caramelized onion, and a cheesy crouton topper. Seriously - what more could you ask for??? You won’t find a lot of recipes out there for Keto French Onion Soup - I know, I checked. The reason is that onions actually contain quite a bit of carbs, so it’s a challenge to keep the overall net carbs down in a soup that’s…well…pretty much made of just onions.
The Crouton Conundrum
These toppers though? I’m not sure what to call them - not quite a toast, not really a crouton, so…???? What I can tell you is that they make the perfect raft for the copious amounts of cheese you are going to add before digging in to this low carb French onion soup! I would also add that these lil toppers are really, really versatile in their own right. I had a bunch in my freezer that I’ve since used to garnish other soups and stews to create a dumpling/biscuit/pie crust situation that was just perfection. I’ve also used these toppers to put my bacon and egg on in the morning like a little open-faced breakfast sandwich.
Carb Considerations
All told, you can have a generous portion of this Keto French Onion Soup, complete with the topper and cheese and still come in at 10g net carbs. It might sound like a lot when you’re shooting for only 20g net carbs per day, but it’s totally doable if you have almost no carbs with breakfast (bacon, eggs, avocado, and coffee are my go to) and a carb light lunch like tuna salad with romaine leaves.
Broth Options
Typically, French onion soup gets its rich flavor from beef broth, which is what I used here. If you don’t eat beef you can substitute chicken broth for a lighter flavor. If you want to make this soup vegetarian or vegan, you can substitute a vegetable broth or stock, but the carbs may be a few grams higher than a broth made with meat. This recipe also includes Worcestershire sauce, which contains anchovies. You can replace it with an equal amount of coconut aminos for a similar flavor that is completely plant-based.
Onion Variety
I used yellow onions, which are traditionally used and give it a nice mellow flavor, but you can use white onions or even red onions if that’s what you have on hand - it will make very little difference in the end result.
Read also: Keto Calorie Counting: A Detailed Guide
General Recipe
This super tasty Keto French Onion Soup is coming at you with a rich, flavorful broth, sweet strands of caramelized onion, and a cheesy crouton topper. Remove the bay leaves, then taste and season with additional salt and pepper if desired. Keep warm until ready to serve, or refrigerate in an airtight container for up to 5 days. Bake for 15 minutes or a light golden brown.
Simple Recipe
My keto French onion soup recipe features caramelized onions swimming in warm broth with crusty bread and melty cheese. Are you ready for more low-carb soup recipes? Simple ingredients. Comfort food at its finest. Surprisingly easy to make. Ready in 20 minutes.
Ingredients
- Butter
- Onions (White onion is preferred, but yellow onions or sweet onions can also work, just not red onions.)
- Granulated sweetener (Just a pinch to balance out the salty flavors.)
- Salt and black pepper
- Beef broth (Essential for French onion soup.)
- Worcestershire sauce
- Keto buns (Traditional French onion soups typically use sliced baguette. To replicate this, we’ve used thinly sliced keto hot dog buns.)
- Gruyere cheese (Another must for French onion soup!)
- Fresh thyme
Step-by-Step Instructions
- Step 1 - Prep.
- Step 2 - Sauté onions. Place a large soup pot over medium heat. Once hot, melt the butter.
- Step 3 - Build the broth. Add the beef broth and Worcestershire sauce and bring to a simmer.
- Step 4 - Prepare the cheesy bread. Slice the keto bread into six thick slices, then slice each in half. Place the twelve pieces of bread onto the prepared baking sheet. Sprinkle the cheese on top.
- Step 5 - Assemble. Ladle soup into small bowls.
Tips
- Can’t find gruyere?
- Don’t cut the onions too thin. Otherwise, you risk them cooking too quickly and shriveling up by the time the soup is cooked.
- Sauté garlic.
- Broil. When time allows, I like to ladle the soup into oven-safe bowls and then place them in the oven on the broiler setting for 30 seconds.
- To make-ahead: Prepare the soup up to three days in advance and store it in the fridge.
What is the difference between onion soup and French onion soup?
The main difference between onion soup and classic French onion soup is that the latter uses beef stock or beef broth. A generic onion soup often uses vegetable broth or sometimes chicken broth.
Detailed Instructions
Preheat the oven to 200C/400F. Line a large baking sheet with parchment paper and set aside. Place a large soup pot over medium heat. Once hot, add the butter to melt. Add the sliced onions, sweetener, and pepper and saute for 8-10 minutes, until tender. Add the beef broth and Worcestershire sauce and bring to a simmer. Once it starts simmering, cover the pot and let it simmer for a further 10 minutes.
While the soup is simmering, prepare the cheesy toasts. Slice your two keto hot dog buns into 6 thick slices and slice each one in half. Place the twelve pieces of bread onto the lined sheet. Sprinkle half the Gruyere cheese over the top. Bake in the oven for 6-8 minutes, until golden brown.
Ladle the soup into small bowls. Add 1-2 pieces of the cheesy toast on top of each soup bowl and sprinkle with extra Gruyere cheese and a sprig of thyme.
TO MAKE AHEAD: Prepare the soup up to three days in advance and store it in the fridge. Before serving, warm it on the stove over medium low heat, then serve with the cheesy croutons.
Expert Tips
Caramelizing Onions
Yup, that’s right - patience. Add gobs of butter to a skillet. For this keto French Onion Soup recipe, we’re going to use 4 tbsp of butter. Now, cook those onions slowly in all that buttery goodness. You want them to be a dark golden brown but not burned. Low heat and lots of time will do the trick. Caramelize the onions (see above).
Serving Suggestions
Top with low-carb bread or a chaffle, cover in cheese, and pop it under the broiler for a few minutes until it is bubbly and brown. Use regular yellow onions. Use proper French onion soup bowls. I love a fresh salad topped with this fabulous Ranch Dressing with a bowl of soup, or if I’m especially hungry, I’ll nibble on toasty Sourdough Chaffles or theses keto cheese breadsticks.
Freezing for Later
Yes! A BIG yes! To freeze it, thoroughly chill the soup. My favorite way to freeze saucy and soupy recipes is by using Souper Cubes! These amazing freezer-safe cubes are perfect for freezing portions of all my favorite soups, stews, and other saucy meals. I freeze them then pop them out and put the rectangular frozen blocks into a zipper-top freezer bag. It makes storing them SOOOO much easier! Where can you find these Soup Cubes?
Keto-Friendly Considerations
Is French Onion Soup keto? It sure is! Start with regular yellow onions, don’t add any sugar (French onion soup shouldn’t have sugar added to it anyway!), and limit the number of onions that you use to control the carbs. And of course, top it with a chaffle instead of bread.
Onion Selection
Yellow onions are what Chef Jenn uses. Sliced thin and caramelized in lots of butter, you won’t need to add any sugar because the natural sweetness in the onions will come out.
Cooking Time
How long does it take to make French Onion Soup? From start to finish, it takes a little over an hour to make this classic soup. It takes time to caramelize the onions, and then it all needs to simmer in the broth.
Quick Recipe
Add the butter to a skillet large enough to hold the onions. Melt the butter over medium heat and slowly caramelize the onions until they're dark brown and soft. Add the garlic and continue cooking for 1 minute. Set aside.
Deglaze the skillet with the red wine and let it simmer for 2 minutes, or deglaze the pan with 1/2 cup of the beef or chicken broth. Scrape all this into your soup pot.
Add the onions, thyme, bay leaf and remaining broth to the soup pot. Cover and simmer for 20 minutes.
Remove the sprigs of thyme and bay leaves and season the soup with salt and pepper. Ladle into bowls and top with a chaffle or low-carb bread and 1/4 cup of cheese. Pop under the broiler until hot and bubbly.
Please note: The nutritional values for this recipe do not include a chaffle or low-carb bread for topping your soup. Nutritional information for this recipe is provided as a courtesy and is calculated based on available online ingredient information. It is only an approximate value. The accuracy of the nutritional information for any recipe on this site cannot be guaranteed. Erythritol carbs (sugar substitutes) are not included in the carbohydrate counts as they have been shown not to impact blood sugar, and they have zero calories and zero carbs.
Why This Recipe Works
French Onion Soup has always been a favorite of mine, and this Keto French Onion Soup delivers on the classic flavors. With a rich, perfectly seasoned broth, garlic, and onions, all topped off with Gruyere cheese, you have a hearty soup that is impossible not to love. Onion Soup is best when the onions are caramelized to perfection. This French Onion Soup recipe achieves that.
Ingredient Substitutions
- Oil: I used avocado oil, but you can use your favorite keto-friendly oil.
- Broth: Homemade beef stock will enhance the flavor, but you can't buy broth if you don't have time to make it.
- Cheese: I used Gruyere cheese, but Swiss cheese will work as well.
- Bread: If you would like to melt the cheese on a keto-friendly bread, you can.
Common Issues
Unfortunately, most French Onion Soups are not keto-friendly. There are several reasons that your onions may not have properly caramelized. The first is that they were sliced too thin. You want them to be at least ⅛" thick.
Thickening the Soup
Yes! Xanthan Gum: Make sure you sprinkle it over the top when adding and whisk well to avoid clumping.
Related Recipes
Add the onion slices and fresh thyme and cook for 10 minutes. Transfer the soup to broiler safe soup crocks. Give it a try and you will see why this Keto Mushroom Soup is a fan favorite. No need to miss potatoes when you have this Keto Cauliflower Soup. This Keto Broccoli Cheese Soup is pure cheesy comfort food.
Final Instructions
Heat the butter and avocado oil in a large saucepan over medium-high heat. Add the onions and thyme and cook, stirring occasionally, for 10 minutes. Reduce heat to medium and cook for another 30 minutes, until the onions are a deep golden brown.
Stir in the garlic and cook for 1 more minute. Add the cooking sherry and cook for 2 minutes, scraping up any browned bits.
Add the broth, coconut aminos, salt, pepper, and xanthan gum. Simmer over medium heat for at least 15 minutes.
Preheat a broiler to high and ladle soup into broiler-safe soup crocks. Sprinkle with cheese. If you like this recipe don't forget to leave a 5 star rating and let me know how it went in the below comments, I love hearing from you!