Sweet Potato Soup with Ginger and Lime

There is a Caribbean beat to this sweet potato soup, which you can make as thick and bisque-like as you wish. Consistency here is determined by the amount of milk you add. Use more or less, to your taste. The finishing touch of grated lime zest brings a burst of flavor to the soup-more than its delicate appearance suggests. At Mangia, citrus, both juice and zest, is used as a powerful flavoring agent.