Sorrel is a very old herb that has been used throughout the centuries in England, as well as the rest of Britain and Europe - especially France. I have called this an English soup, as it does not contain any egg yolks, as French Sorrel soup often does. It can be served chilled or hot, and is also delicious made with a combination of sorrel, watercress and other green herbs. You must try to use the small round tipped sorrel leaves, as the large pointed leaves are very bitter! Sorrel is a purgative and an excellent detoxification herb, so you can enjoy your soup as well as cleansing yourself!! Garnish with croutons and finely chopped sorrel leaves.