Six hour onion soup

Onion soup from three ingredients; onions, water, salt. It’s not only possible but absolutely worth the six hours it takes to make. The finished soup is clear, dark, sweet and rich, with tiny slivers of onion floating in it. Best served with a giant sourdough crouton topped with cheese and grilled.

For two people:

  • 8 large onions peeled and sliced into half moons
  • Salt
  • Water

To serve:

  • Thick slice of sourdough
  • Nice melty cheese like Gruyere

In a high sided pan on a low/medium heat, fry the onions with a lid on for around an hour, stiring every five minutes. During this first phase the water will render out of the onions and they will gently stew in their own juices. The juices will be almost gone after an hour.

Drop the heat to low, leave the lid halfway on the pan and continue cooking for another two hours, stiring every twenty minutes.


After the third hour the onions will start sticking to the pan and caramalising. Drop the heat the the lowest setting and continue to cook for another two hours, stiring every twenty minutes.


The onions will eventually be very dark brown, about 10% of their original volume and extremely sweet. Pour in a liter of water and bring to a gentle simmer. Start seasoning the soup with salt, a little at a time over a thirty minute period and keep tasting until you’re happy with the flavor.


The soup is now finished. You could go nuts and add some black pepper. You may find the soup a little sweet from the caramalisation on the onions, you can fix this with a tablespoon of red wine vinegar.

To finish the dish cut the sourdough to about the size of your serving bowl and toast on both sides. Pour the soup into the bowls, top with the toast and then the melty cheese. Put the bowls under a hot grill for 2-3 minutes until the cheese is bubbly and brown.



3 thoughts on “Six hour onion soup

  1. This is brilliant. Onions, water and salt. I’ve cooked onions down for a long time, but never that long. I have to try it.


    1. Well yeah you’d normally use a little butter to start the onions off but if you want zero calories use 2 or 3 tbs water to lubricate things until the onions start giving off their juices.


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