This is a real winner - quick, simple, cheap and tasty. Chorizo and butterbeans is a classic combination, the sweetish blandness of the butterbeans seems to accentuate the rich spiciness of the chorizo.
I usually make this soup for two but if you're cooking for more just add extra ingredients as required. To start, finely chop a red onion and soften it in olive oil. Add some chopped garlic, you can be generous with this, or not, depending on your preference for garlic. Put a couple of sprigs of thyme in if you have them. If you don't have thyme you could use bay 2 or 3 bay leaves, oregano would be nice as well.
When the onions and garlic have softened and have started to give off that wonderful aroma that cooking onions always do turn up the heat and add some chopped chorizo. There's no need to be shy here, if you like chorizo put plenty in. The better the chorizo the better the taste of the soup, so use as good as you can get.
When the red oil is coming out of the chorizo add a tin of drained butterbeans, if cooking for two, and pour on enough boiling water to cover the beans. A bit extra won't hurt, but make sure you use enough water or there won't be a lot of liquid to your soup. Cook for about 10 minutes.
Before serving add a good amount of fresh parsley and a squeeze of lemon, then season and serve.
It's something I cook again and again because its easy and very tasty. You can use it as the basis for some other dishes as well. You could use chick peas instead of butterbeans and add some squid for something a bit fancier. Or some chicken for a more filling soup. Merguez sausages could be used instead of chorizo and you could pep things up with a dollop of harissa and a stir of sour cream. Mmm, I'm going to have to get hold of some merguez sausages and give that a go myself.