Heat the oil in a large pan over a medium heat. Add the leeks and onion and cook for 5 minutes until soft. Stir in the sweet potato and cook, stirring frequently, for a further 10 minutes.
Add vegetable stock, cover and bring to the boil.
Reduce heat and simmer for 25 minutes or until the sweet potato is soft and tender.
Season with salt and pepper and remove from the heat to cool for 5 minutes.
Using a blender or hand blender pulse the mixture until smooth.
Heat the ProZero in the microwave or on the hob, then add to the soup and continue to simmer (do not boil).
Garnish with chopped chives and serve.
Pour leftovers into a tupperware container for a quick and easy lunch, ideal to take to work or school!
ProZero is a food for special medical purposes and must only be used under strict medical supervision.