I’ve long had trouble getting onions to caramelise properly, often when following recipes ending up with an unevenly browned or oily result. But if I want to make my very favourite soup, and get a proper depth of flavour I have to master it!
After a bit of experimentation, I think my problem has been too low a heat under the pan. Recipes that recommended leaving the onions on a low heat and stirring occasionally just don’t work for me!
This method, using a medium heat and very little oil results in a much better colour and flavour than I’ve achieved previously, which is perfect for French style onion soup.
Utilising the onion skins to colour some of the water helps so much with the colour of the soup, but don’t leave the skins in there too long or it can be bitter.
I’ve used vermouth to deglaze the pan after caramelising the onions, but brandy or white wine would be good too.
I love a great big bowl of this soup as a main meal, so this quantity would do two servings in that case, or four as a light meal.
serves 2 to 4
3 onions (about 500 g before peeling), thinly sliced, reserve the inner skins
1 tbsp oil
3 tbsp vermouth
1.4 l water
1/2 tsp marmite, or yeast extract
1 tsp vegetable stock powder or 1/4 of a stock cube
1/4 tsp dried thyme
1/4 tsp ground fennel seed
2 bay leaves
1/4 – 1/2 tsp sugar
1/2 tsp potato starch, slaked. This is optional but it does give the soup some body
Heat the oil in a large saucepan on a medium heat.
Add the onions to the pan and cook, stirring every 2 – 3 minutes for 30 minutes until dark golden and tangled. If the onions start to catch, add a tablespoon of water and before it evaporates quickly scrape the sediment off the bottom of the pan. The sediment will add extra colour and flavour to the soup.
While the onions are cooking, put the onion skins and about 600 ml of the water into a small saucepan and bring to the boil. Turn the heat down and simmer for 3 minutes. The onion skins should have given the water a lovely golden colour.
When the onions are caramelised, add the vermouth to deglaze the pan. Stir vigorously as the vermouth bubbles and reduces.
Add the onion skin stock, through a sieve to catch the skins.
Then add the rest of the water, the marmite, stock powder, thyme, fennel and bay leaves. Mix well and bring to the boil. Turn down to a simmer and taste the soup. Add the sugar, starting with 1/4 tsp. If your onions are particularly sweet you may not need it all.
Simmer the soup, partially covered, for 45 minutes, it will have reduced a bit.
Add the potato starch, if using, and mix well. Season with pepper to taste, and serve.