Discard any tough stalk ends from the cabbage and roll the leaves up tightly. Using a large knife, shred the cabbage as finely as possible.
Heat the oil in a large saucepan and gently fry the onion for 5 minutes. Add the potatoes and cook, stirring occasionally, for 10 minutes. Stir in the garlic and cook for a further 1 minute.
Add the stock and bring to the boil. Reduce the heat and simmer gently, covered, for about 10 minutes until the potatoes are tender. Use a potato masher to lightly mash the potatoes into the soup so that they are broken up but not completely puréed.
Stir in the beans, shredded cabbage and coriander and cook gently for a further 10 minutes. Season to taste with salt and pepper.