Heat the olive oil in a saucepan and fry the sweet potato, carrots and carrot tops over a low heat for 5-10 minutes, or until softened.
Pour in the vegetable stock, bring to the boil, then reduce the heat until the mixture is simmering and simmer for 10 minutes, or until the vegetables are tender.
Add the coriander, then blend the mixture with a stick blender until smooth. Season, to taste, with salt and freshly ground black pepper.
