Heat the oil in a large pot over a medium/low heat, then add the onions and cook, stirring often, for 5-7 minutes or until soft but not browned. Stir in the garlic and ginger and cook for a further minute.

Stir in the sweet potato, carrot and cook, stirring for 2 minutes.

Add the vegetable stock and miso paste, stir well, increase the heat and bring it nearly to boiling. Reduce the heat and simmer for 15 minutes.

Stir in the butter beans, then cook for a further 5 minutes or until the vegetables are all soft and cooked.

Either leave the soup chunky, or use a hand blender (or carefully ladle the hot soup into a blender) and blitz until smooth, or blend just half of the soup.