Vichyssoise is a simple soup prepared from potatoes and leek, and served cold. This is a great starter to a picnic or any summer entertaining, it is easily jazzed up with a few simple additions (see these at the end of the recipe). For ease you can prepare it well in advance and freeze it and simply defrost on the day. I serve the soup with freshly baked herb and rocket focaccia but you can make or buy your favourite bread if you wish.