French Onion Soup
You wouldn't believe this restaurant-worthy French Onion Soup is slimming-friendly. It's deliciously rich and hearty, with sweet caramelised onions, and it's less than 100 calories per bowl!
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NutritionPer Serving
- Calories93
- Carbs16g
- Protein3g
- Fat1.4g
- Saturates0.6g
- Sugars9.7g
For the full list of ingredients and comprehensive instructions, please see the recipe card at the end of this post. Before you scroll, there’s important stuff to know in the blurb!
French Onion Soup is one of those classics that’s all about big flavour from simple ingredients. As the onions cook down, they turn beautifully caramelised, creating a rich base for the soup.
We love this recipe as a way of packing plenty of veg into a satisfying dinner or lunch. It’s super straightforward to make, ideal for making a big batch for having tasty soup on tap!
It’s also great topped with a toasted slice of wholemeal bread and a sprinkle of reduced-fat cheese. Grill the cheese until golden and bubbling for that delicious finish that makes it feel restaurant-worthy.
What diets is this French Onion Soup suitable for?
This French Onion Soup recipe is suitable for dairy-free diets. It can easily be made gluten-free and vegetarian, as long as you swap out the following ingredients for gluten-free versions:
- Stock cubes
- Worcestershire sauce
Remember to take extra care when you’re cooking for people with allergies. Use separate utensils, cookware, and preparation surfaces.
Do you need any special ingredients to make French Onion Soup?
This French Onion Soup is dead easy to make, with no fancy kitchen gadgets. You’ll find everything on your local supermarket shelves.
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How many calories are in this French Onion Soup?
There are 93 calories per portion in this French Onion Soup, which means it falls into our Everyday Light category. These are all dishes under 400 calories, ideal for when you’re after a lighter bite (just like the category name suggests!), and they fit with diet plans like Weight Watchers if you’re calorie counting.
As a guide, an average man needs around 2,500kcal (10,500kJ) a day to maintain a healthy body weight. For an average woman, that figure is around 2,000kcal (8,400kJ) a day. Obviously, if your goal is to lose weight, then you might want to adjust these slightly. You can read more about these recommendations on the NHS website.
Step 1
Spray a large saucepan with low-calorie cooking spray, and set on a medium heat. Add the onions and garlic, and fry for 10 minutes. Don’t stir it too much, as you want the bottom to brown and to give the soup its rich colour.
Step 2
Add the balsamic vinegar and Henderson’s relish, and stir. Pour in all of the water, then add the stock cubes and vegetable stock pot.
Step 3
Continue to simmer for 25-30 minutes.
Step 4
Serve the soup with a garnish of your choice!
What could I serve with this French Onion Soup?
This French Onion Soup works really well when served as a starter with the following main, side, and dessert:
How do you know when French Onion Soup is cooked?
You’ll need to cook this French Onion Soup for half an hour on the stove top or for 20 minutes in your Instant Pot.
As per UK food safety guidelines, always cook meat until it reaches 75ºC and stays at that temperature for at least two minutes. This is to keep you and whoever it is you’re cooking for safe.
Can I cook this French Onion Soup any other way?
Yes, you can! If you prefer, this recipe comes together beautifully in your Instant Pot — which takes around 20 minutes.
How long can you keep French Onion Soup in the fridge?
Once you’ve served up your French Onion Soup, ideally you should eat it within 4 hours.
If you do allow any leftovers to cool, be sure to refrigerate in a container with a lid. You can keep leftovers of French Onion Soup in the fridge for approximately 3 days or so.
Can I freeze French Onion Soup?
Yes you can! This recipe can be frozen, just remember to do the following;
- Freeze it as soon as it’s cold enough.
- Use a container or bag that’s suitable for freezing.
- Don’t forget to add a label with what it is, and on what date you put it in the freezer!
How do I reheat French Onion Soup?
From chilled: Place in a microwave-proof container with loosely fitting lid, and heat for 4-7 minutes — until piping hot.
From frozen: Allow to defrost fully, then heat covered in the microwave for 3-5 minutes. Give it a good stir. Cook for a further 5-7 minutes, until piping hot.
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French Onion Soup
You wouldn't believe this restaurant-worthy French Onion Soup is slimming-friendly. It's deliciously rich and hearty, with sweet caramelised onions, and it's only 93 calories per bowl!
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Prep Time
10 MINS
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Cook Time
30 MINS
- KCals 93
- Carbs 16G
Instructions
- Spray a large saucepan with low-calorie cooking spray and set on a medium heat. Add the onions and garlic, and fry for 10 minutes. Don't stir too much, as you want the bottom to brown to give the soup its rich colour.
- Add the balsamic vinegar and Henderson’s relish and stir. Pour in all of the water, then add the stock cubes and vegetable stock pot.
- Continue to simmer for 25-30 minutes.
- Serve the soup with a garnish of your choice!
Looking for Slimming World Syns or Weight Watchers (WW) Points?
With ever-changing plans and point calculations, we have made the decision to remove WW Points from the website - referring to your individual plan or advice from your consultant is always going to give the most accurate results.
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25 comments
See what others have to say
Paul FosterTuesday 24th February 2026
Is it Oxo type stock cubes – each makes 190ml stock, or Knorr type – each making 500ml?
HollyWednesday 25th February 2026
Hi Paul, this recipe uses 1 vegetable stock pot and 2 beef stock cubes with 1 litre of water, hope that helps!
Paul FosterWednesday 25th February 2026
That didn’t answer the question!
HollyTuesday 31st March 2026
Any beef stock cube and vegetable stock pot that you prefer using with 1 litre of water, hope that helps!
Leanne AldersonTuesday 4th May 2021
Do u have to sautee thè onions and gsrlic before putting in a slow cooker
HollyMonday 10th May 2021
Hey Leanne, if you are converting this recipe to a slow cooked yes i would suggest frying the onion and garlic before adding it to the slow cooker pot. Have a look at THIS article you may find it useful when converting recipes to slow cookers. Hope that helps!
KerrySunday 31st January 2021
Hi all! I made on the hob, simmered for 30-40mins and it tasted amazing 😊 I made toasted croutons and also added a sprinkle of grated cheese. Absolutely delicious! 😍
HollySunday 31st January 2021
Hi Kerry, so glad you enjoyed the French Onion Soup!
MissySunday 23rd August 2020
How long would I do this for on the hob, please?
HollyWednesday 26th August 2020
Hey Missy, it’s not something we have tried but I would suggest cooking the onions until soft for 10 minutes then adding balsamic vinegar and Worcestershire sauce. Pour in all of the water, add the beef stock cubes and vegetable stock pot. Cover with a lid and simmer for 30 minutes. Let us know how you get on!
Denise MurphySunday 8th March 2020
Can I just use a large saucepan
Steve CowderoyWednesday 6th May 2020
Hi Denise, yes you can definitely cook this delicious soup in a large saucepan. just make sure you caramelize your onions well before adding your stock. Hope this helps, please let us know how you get on.
NiaThursday 17th January 2019
Could I make this using vegetable stock cube instead of beef and still have the flavour? (Vegetarian) thanks
Claire blythSunday 14th October 2018
Hi can you do this in a soup maker ???? thanks.
ShellFriday 13th July 2018
This may sound stupid but what is a ‘vegetable stock pot’? Also can you freeze this soup?
JadeMonday 16th April 2018
Hi
I love French onion soup, but don’t have a sauté pot. Do you think it could be done in a soup maker?
Thanks ☺️
Jennifer JohnsonFriday 2nd March 2018
hi, how long will this keep in the fridge please.
AislingMonday 19th February 2018
Hi this looks delicious! Just wondering what the cheesy topping is? Thanks.
Sarah BradshawTuesday 9th January 2018
Could you do this in a soup maker or would not be the same without frying the onion and garlic? Can you recommend a cheaper version of the instant pot? I looked at them on Amazon but very expensive! There are alternatives but which one?!! Haha! Thanks in advance. ????
WendyloisFriday 12th May 2023
I’ve made this in my soup maker but I browned the onions first as this adds flavour. Then put it in the soup maker with the rest of the ingredients and cooked on the ‘chunky’ setting.
SharonFriday 12th May 2023
Hi Wendylois, thanks for sharing your experience of making our French Onion Soup in a soup maker, it’s appreciated.
SharonMonday 27th November 2017
Looks lovely. How would you do this in the slow cooker please?
JessicaTuesday 7th November 2017
This looks so good, it’s my favourite soup – can’t wait to try it!
TracySunday 5th November 2017
Can you provide the cooking instructions for someone with no instant pot please?
CeriSunday 5th November 2017
How would you make this on the hob please?? 🙂
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