French Onion Soup (keto)

If you are looking for a delicious but easy keto French onion soup, I have the recipe for you today. Full of caramelized onions and a savory broth, topped with gooey melted cheese. And I have a low carb solution if you want the toasted bread under the cheese. This tasty soup is also low calorie with only 125 calories!

Check out this post with over 50 delicious soup recipes.

I love French onion soup but have never made it until recently and I was surprised at how easy it was. However I wanted to make low carb so I had to figure out a low carb solution for the bread or toast that lies under the cheese. And today I figured out the perfect low carb option.

This keto French onion soup is everything you would want from the sweet caramelized onions, savory broth, toasted bread and ooey gooey melted cheese on top. It was delicious! One serving with 5 keto croutons and 2 tablespoons of cheese had 8.3 grams of net carbs, 4.5 grams of fiber, 7.2 grams of protein and 125 calories!

How I keep this French onion soup low carb.

The two things that add the most carbs to classic French onion soup is the large amount of caramelized onions and the toasted crispy bread layer which is usually a slice of French bread baguette. So I still used a good deal of onions but you could cut that down on them if you wanted to save a few more carbs.

And for the French bread baguette slices I used keto croutons! I’ve made them before and now I keep a stash on hand for my salads. I’ll show you how to easily make them below.

Also some people use flour to make a roux and thicken the soup. I just eliminated the flour and it was fine. And some use sherry or red wine but I substituted with vinegar and it worked like a charm.

Recipe ingredients and substitutions.

The simple ingredients I used were onions, fresh garlic cloves, butter, apple cider vinegar, dried thyme, Worcestershire sauce, beef broth or stock and beef Better than Bouillon base.

If you want to add cheese, I used shredded gruyere cheese and Swiss cheese blend you can find at Aldi. Other cheeses to try are just Swiss, asiago, gouda, or even mozzarella. You want a melty and flavorful cheese so mozzarella would be my last choice but it’s doable.

• onions – I used regular yellow onions but you can white onions if you want. You can use less onions if you want to cut down on the carb.
• beef stock and Better than Bouillon – You can use beef broth, chicken broth or even vegetable broth if you want. I do recommend the Better than Bouillon as it adds so much flavor to soups. You can substitute with regular bullion or another brand of base. If you eliminate it altogether just taste and adjust the seasoning. You may have to add a bit of salt and try to use stock instead of broth as it has more flavor.
• Worcestershire sauce and apple cider vinegar – Again these both add flavor and while some people use sherry or wine and I used the apple cider vinegar instead. You could use regular white vinegar instead or red wine or sherry vinegar would be great. I would not substitute the worcesetershire sauce.
• fresh garlic cloves and thyme – These both add flavor and I would keep both them. I used dried thyme and not fresh but you can always garnish with fresh thyme sprigs.

If you want to add the baguette layer but keep it keto.

To make the keto croutons to substitute for the French baguette you need a keto friendly bread. I bought mine at Aldi and they seem to have it regularly. You also need butter, garlic powder, Italian seasoning and cooking spray.

This keto bread has no net carbs because it’s very high in fiber. I personally don’t love the flavor as a sandwich bread but then again I don’t eat many sandwiches. It is however excellent for croutons.

I’ll show you how to make the croutons below but I do have a whole post on it.

How to make French onion soup.

If you want to make the keto croutons you have to make them at least the day before. Just get a baking sheet and layout 4 pieces of keto bread and let them sit out uncovered overnight. The next day cut each stale piece of bread into 16 pieces and toast according the directions in step 4.

Step 1: Heat up a soup pot to medium high heat and add the butter. When the butter has melted add the sliced onions and cook for a few minutes and then turn the heat down to medium. Saute until the onions are browned and caramelized. This sautéing may take up to 25 minutes.

Step 2: Next add the beef broth or stock, Better than Bouillon base, crushed garlic, apple cider vinegar, thyme and Worcestershire sauce. Mix well and bring to a simmer. Cover and cook for 10-15 minutes more.

Step 3: While the soup is cooking you can make the keto croutons if you want to use them.

Step 4: To make the keto croutons: Heat up a skillet to medium heat. Add the butter and when it melts mix in the spices then add the cut up pieces of stale bread. Quickly mix around to coat the bread cubes.

Continue to cook until toasted on all sides. I like to spray them with cooking spray as you toss them so that they are evenly coated. You could also use more butter but I didn’t want to.

Step 5: If you don’t want to make the croutons, you can just ladle the soup into bowls and eat it as is for a tasty low carb soup. Or skip the croutons and just add cheese to the top and place in the oven under the broiler to melt.

Step 6: To assemble the soup with bread and cheese, get out a baking sheet and add the crocks, ramekins or oven safe bowls. Ladle in the soup and then add a few croutons (if using) and about 2 tablespoons of cheese. You can use more if you want as well.

I used a gruyere cheese and Swiss cheese blend I buy at Aldi all the time. You can also use asiago cheese, parmesan cheese, gouda and even mozzarella. But I personally like the Swiss gruyere blend. 

Place the baking sheet in the oven under the broiler and when the cheese is brown and bubbly take out and serve.

Store leftover French onion soup in an airtight container. Please scroll down for the printable recipe card.

As I mentioned above you can eat it as is for a low calorie soup or add the croutons and cheese for a more decadent dish. This keto French onion soup recipe makes about 8 servings so we ate this for a few days and it was delicious!! I hope you give it a try.

With the way I prepared my bowl, I used 5 keto croutons and 2 tablespoons of gruyere/Swiss cheese blend and the macros are: 8.3 grams of net carbs / 4.5 grams of fiber / 7.2 grams of protein / 125 calories

The nutritional information for 1 serving without keto croutons is 47 calories / 0.3g fat / 9.6g carbs / 1.4g fiber / 1.9g protein = 8.2g net carbs

The nutritional information for 1 croutons is 5 calories / 0.3g fat / 0.6g carbs / 0.6g fiber / 0.3g protein = 0g net carbs