1Heat the butter or oil in a medium saucepan over medium heat. Add the carrot, garlic and onion and saute till softened.
3Add the chopped parsnips and sweet potato, then add water to cover. Bring to the boil, then turn down to a simmer. Simmer until the vegetables are tender, about 20 minutes.
5Take the soup off the heat. In small batches, carefully puree the soup in a blender or food processor (or use a stick blender right in the pan). It should be rather thick.
7Back in the pan over medium heat, add the milk of your choice and simmer for a further 5 minutes. Serve with fried bacon if you like.