Keto French Onion Soup Recipe

Updated: March 15, 2022

This keto French onion soup will remind you of the classic bread-topped comfort food – but with far fewer carbs! By keeping the number of onions in check and topping your soup with a chaffle instead of bread, you end up with all the same flavors and textures in this dish in a way that still fits your keto diet.

If there’s one recipe that my wife loves ordering at restaurants, it’s French onion soup. She gave this dish a big thumbs up, so you know it’s a winner!

A bowl full of keto french onion soup next to a napkin and spoons

Are onions low-carb and keto-friendly?

You’re probably wondering how we can provide an onion soup recipe that contains carbs! Believe it or not but onions are actually keto-friendly as they are often used as a flavor enhancer. As a result, you end up using a small amount, which will keep you from drastically increasing your daily carb intake.

How many net carbs are in French onion soup?

You can have onions on keto, but you will have to make sure you eat it in moderation, which you can do by using onions based on weight instead of amount. For instance, 400 grams of sauteed onions is equivalent to a large onion and has 31.44 grams of carbs but only 6.8 grams of dietary fiber. This puts the onion at 24.64 grams of net carbs, which is obviously a no-go on a ketogenic diet. Our keto onion soup recipe, on the other hand, is a healthy pick that you can enjoy time after time without fearing that you’ll be kicked out of ketosis.

Traditional French onion soup

Is French onion soup keto? Well, that depends. The traditional version isn’t, but the keto version is. The classic dish is a no-go on a keto diet as the carbs in French onion soup come from the thick bread that is used to prepare it. Onions, which I mentioned can be consumed on keto, are used in greater quantities, often including as many as five onions for a meal. This means that not only are you increasing your carb intake, but you’re also most likely to go above your daily sugar intake.

How to make keto French onion soup

This low carb soup has three components – the base of the soup, the chaffles for topping, and then the cheese to add on top of that.

Soup base

Here are the ingredients you’ll need to make the keto soup base:

  • Butter
  • Onions
  • Garlic
  • White wine
  • Beef stock
  • Bay leaf
  • Thyme

All you’ll do is slice up your onions and then sauté them in butter at low heat for a solid 20-30 minutes. Don’t try to rush this process; you want to cook them “low and slow” so it brings out all the natural flavor in the onion. They’ll look like this when you start cooking them…

Onions at the start of cooking in a pot

And then they’ll start to get more golden brown towards the later half of cooking (forgive the bad photos; my kitchen lighting isn’t overly great)…

Onions towards the end of cooking in a pot

After that, you’ll add in a little garlic and deglaze the pot with the wine. Then add in your stock, bay leaf, and thyme and let it all simmer for about 10-15 minutes.

The total time to make the base does take a while, but as you can see, it’s pretty hands-off and only requires minimal ingredients.


While the base of the soup is finishing up, you’ll make the chaffles to go on top. If you haven’t heard of chaffles before, essentially they’re a simple blend of egg and cheese that crisps up amazingly well in a waffle maker!

For this recipe, we used our new Dash waffle maker (<– amazon affiliate link; we earn a commission on qualifying purchases). This is a mini waffle maker that works really well for chaffles. The basic recipe I use frequently is 1/4 cup cheddar, 1/4 cup mozzarella, and 1 egg to make two mini chaffles. You can use those proportions for breakfast waffles, making waffle sandwiches, etc. For this recipe, we’re tripling those basic proportions so we can make 6 mini chaffles – one for each soup serving.

Dash mini waffle maker

Cheesy topping

When your soup and chaffles are done, you can transfer the soup to small ramekins and top with the chaffle. Then add about an ounce of shredded gruyere cheese on top, and broil until it’s all melted.

Grab a spoon, dig in, and enjoy!

Spoonful of low carb french onion soup next to a ramekin of it

Helpful recipe tips

  • I recommend weighing your onions for the most accuracy with this recipe. I originally planned to use 3-4 onions, but when I weighed them it was far heavier than I expected (which would have pushed the carb count over an ideal amount). I reduced it to two large onions, which ended up weighing a little over a pound (18 ounces). You want to be around 1-1.25 pounds for this recipe, in order to keep the carb count in check. This might look like 2-3 large onions, or 3-4 medium onions, depending on the specific size.
  • When you make your chaffles, don’t overfill the mini waffle maker! When we photographed this, I had a helper in the kitchen (ehhhm, my wife) that dumped way too much batter into the mini maker – which causes the batter to drip out all over the sides and make a mess. If you put too much in, you’ll also run out of batter before you’ve got enough chaffles (like we did, haha). We only had enough eggs on hand for one go at the recipe, so you can see that we had to chop our chaffles in half for these photos – as you can see below, haha. 😉
Half a chaffle on a bowl of keto french onion soup
  • If you don’t have a mini waffle maker, you can easily make this in a regular Belgian waffle maker too. I would split the batter in half and do two big waffles, and then split each of those into thirds for topping your soup.
  • Only make as many chaffles as you need for that evening’s dinner. They don’t hold up as well in the soup for reheating, so it’s best to make them as needed.

Nutrition breakdown for low carb French onion soup

This soup contains 29 grams of fat and 8.9 grams of net carbs per serving. It’s a little higher in net carbs than I might aim for at all meals, but if you’ve got some lower net carb meals at other points in the day – you can easily still stay below 20 grams of net carbs total for the day.

The macronutrient breakdown is as follows:

  • 67% fat
  • 9% carbs
  • 23% protein

In addition to having an acceptable keto meal breakdown, this soup also packs in quite a few vitamins and minerals. Because of the cheese, you’re getting a good helping of your daily calcium needs for bone health. You’ll also get 20% of your daily Vitamin A requirements (for healthy eyesight) and more than 15% of your daily zinc needs (involved in immune health).

Other keto soup recipes

If you’re looking for more keto soup recipes, be sure to check out one of these tasty options from fellow bloggers:

I hope you enjoy this keto French onion soup! If you get a chance to try it, we’d love for you to leave a recipe rating or comment below.


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A bowl full of keto french onion soup

Keto French Onion Soup

Yummy Keto Cooking

0 ratings

This keto French onion soup will remind you of the classic bread-topped comfort food – but with far less carbs!

Prep time

Cook time

Total time

15 mins

50 mins

65 mins



1 serving

392 kcal



  1. Add the butter to a large pot over medium heat. Add the onions and sauté for about 20-30 minutes, stirring frequently, until caramelized.

  2. Add the garlic and cook for another minute. Pour in the wine and let it simmer for 2 minutes.

  3. Stir in the beef stock, bay leaf, and thyme. Simmer for about 10-15 minutes.

  4. While soup is cooking, make your chaffles. Mix together the mozzarella, cheddar, and egg. Spoon out enough batter to just fill a mini waffle maker. Cook until done. Repeat with the remaining batter (this should make about 6 small chaffles).

  5. Discard the bay leaf and thyme, then ladle your soup into oven safe dishes. Place a chaffle on top of the soup and then add some shredded Gruyere cheese on top of that. Broil for 2-3 minutes until cheese is melted. Enjoy!


Cuisine: French - Course: Soup - Keywords: keto french onion soup, keto soup, keto soup recipe, low carb, low carb french onion soup, yummy keto cooking