Heat the oil in a large saucepan, add the onion and cook for 3 minutes. Add the chorizo and fry until golden. Stir in the garlic, cumin and tomato purée until well coated and cook for a further 1 minute.
Add the beans and liquid, stock, oregano and chipotle sauce to taste. Bring to the boil, then reduce the heat and simmer for 15 minutes. Season to taste.
Ladle the soup into serving bowls. Sprinkle over the chopped chilli and top with a lime wedge.