Hearty bean and chourizo soup

Last night, while driving home, I had a hankering to make a huge pot of soup, so I could bring in a bowl every day during this cold weather. I stopped in at the William Nicol Pick 'n Pay and ambled around the aisles, tossing in what I thought would work. When I got home, I hauled out the slow cooker and got cracking.

This soup is kind of free-flowing; I guess you could ring the changes with whatever you like, really. I may give some ideas at the end of the recipe.

What you'll need:
Two large Chourizo, sliced
One or two large onions, coarsely chopped
A tablespoon of garlic
A handful of leeks, coarsely chopped
Three large carrots, peeled and sliced into rounds
Three large soup celery stems plus leaves, coarsely chopped
A double handful of parsley, chopped
Three medium potatoes, peeled and diced into thumbnail-sized pieces
A tin of tomatoes in juice
A tin of mixed beans
A tin of chickpeas
A small tin of tomato puree
Two litres of stock of your choice (I mixed beef, vegetable and garlic & herb)

Fry the chourizo, garlic and onion until browned, adding a tablespoon of water at a time to prevent sticking. Toss into the slow-cooker.
Fry the leeks, parsley and celery until wilted; toss into the slow-cooker.
Add the rest of the ingredients and mix well, until the tomato puree has dissolved.
At this point you can add about a teaspoon of sugar to cut the acidity of the tomatoes, plus salt and pepper to taste.
Cover the slow-cooker and set for 10 hours on low heat.

Ring the changes with spinach, kale or other leafy greens, red and yellow peppers instead of onions, bacon or smoked chicken breast instead of chourizo, and pretty much any other kind of legume you might desire. I imagine that courgettes and other squash would work a treat and I will be making a version with parsnip and / or turnip at some stage. Although I didn't have any available last night, I sometimes put the rind of an almost-finished piece of parmesan or pecorino into the soup to add some robust flavour.

Serve hot with crusty bread and lashings of butter.