Slow cooker French onion soup

Slow cooker French onion soup recipe

Here we go, here’s a recipe that’s a little more suited to the current weather (um, I guess it’s true, us Brits really do talk about weather all the time). What could be better when it’s bitterly cold and snowy outside than a steaming bowl of French onion soup? Actually, there is one thing better – French onion soup that’s been made in the slow cooker with barely any effort. Win!

Slow cooker French onion soup recipe

When I find a recipe I like, chances are I’ll Pin it, then forget about it, and won’t get around to actually making it for months, if ever. However, as soon as I saw this recipe on Kitchen Simplicity I knew it would be one I’d be trying very soon. And I was glad I did – it was seriously easy, and was perfect for lunch, topped with a cheesy crouton (I used mozzarella because it’s what I had to use up, but gruyère is more traditional).

Slow cooker French onion soup recipe

If you want to make this soup vegan, stick to a cheese-free crouton, or use vegan cheese. I’d recommend the latter, since that melty crouton is not something I’d want to miss out on.

Slow cooker French onion soup recipe

Fancy a bowl of warm soup, but French onion isn’t your thing? You could also try roasted red pepper and spinach soup with orzo, veggie pot pie soup, potato and spring onion soup, or lentil and bulgur soup with lemon and parsley. They’re all ace.

Slow cooker French onion soup
Prep time
Cook time
Total time
Recipe type: Soup
Yield: 3
  • 25g butter
  • 4 onions, halved and sliced
  • 3 cloves garlic, minced
  • 2tbsp balsamic vinegar
  • 2tbsp sugar
  • 3tbsp plain flour
  • 200ml vegetarian beer
  • 350ml vegetable stock
  • 1tsp dried thyme
  • Black pepper
  • White baguette, sliced, to serve
  • Cheese, to serve (I used mozzarella, but gruyère is more traditional)
  1. Turn the slow cooker on high, and add the butter, onions, garlic, balsamic and sugar. Mix well, and cook for 3 hours, stirring every hour or so.
  2. Add the flour, and mix. Then add the beer, stock, thyme, and plenty of black pepper, and mix well again. Cook on high for a further 3 hours.
  3. To serve, spoon the soup into heat-proof bowls, and top with a slice of bread and some cheese. Grill (broil) for a few minutes, until the cheese is crispy. Alternatively, if you don't have heat-proof bowls, lay the bread on a baking sheet and top with the cheese. Grill (broil) for several minutes, and then serve the cheesy bread on top of the soup.

To see other versions of this soup, see Kitchen Simplicity and How Sweet It Is.


  1. says

    So funny, I just made French Onion Soup for my hubby yesterday! It’s like his favorite soup, but I still only make it a couple times a year. I love the idea of making it in a crockpot though, that would make things much simpler!

  2. Jess says

    Last night I made a French Onion Soup for the first time and I was rather underwhelmed. The flavor combination of this one seems spot on and I can’t wait to try it! Just hand wrote it on a card and filed it in my recipe box – I’m a bit old-fashioned in that way.

  3. says

    Too Sweet. Thank you for the recipe however, I didn’t know if I was eating desert or dinner. In all fairness I do not have a sweet tooth- however my husband does and he was the first to mention that it was too sweet. Next time I will leave the 2 tablespoons of sugar out. Happy Cooking.

  4. Jana A says


    thank you so much for this recipe, we enjoyed this soup very much. I have made an onion soup before and it took ages to do. I love slow cooker it made it so much easier.

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