Soak your beans overnight. Discard the water. Cover with fresh cold water and bring to boil. Boil for 30 minutes.
Heat olive oil over a medium heat. Sweat onions, leek, carrots and garlic for 15 minutes.
Add your sliced chorizo and turn up heat a little. Now the spices and cook for 5 more minutes.
Now throw the chopped tomatoes in. And, once the beans are getting going, tip the contents of the pan, both beans and boiling cooking water - carefully - into the stew. Season well with salt and pepper. Let it simmer for 2 1/2 - 3 hours.
Serve with crusty bread, fresh parsley, more olive oil and seasoning.