Green is my favourite colour, but that is not why this soup is good. This is certainly a very English-feeling soup and one I can only describe as gentle and calming. The prawns are not a necessity, but are nonetheless happy here, and the pink and green are very pretty together.
This soup should be eaten cold and preferably outside on a hot day. If there is no sorrel available, the soup is still good without it - but add a squeeze of lemon.