Melt the butter in a saucepan, add the ginger and fry gently for 1 minute. Roughly chop the remainder and add to the pan with the parsnips. Fry gently for 2 minutes.
Add the stock and bring to the boil. Reduce the heat, cover and simmer gently for 15 minutes until the parsnips are tender.
Transfer the soup to a food processor or blender and process until smooth, or leave the soup in the pan and use a hand-held electric blender.
Return the soup to the pan,
Add the cumin and stir well. Warm the soup through for a minute, then season to taste.I served my soup with a dollop of greek yoghurt and a sprinkling of cayenne pepper, but you could use creme fraiche and scatter some finely sliced spring onion on top.