Put the first four ingredients in a blender and blend until smooth. Pour into a large chilled jug and top up with sparkling water. Frosted fresh mint leaves are suitable for decoration, if liked.
An alternative version of this drink, for which you will have to think of another name, can be made from concentrated grapefruit juice, lime or lemon marmalade and a couple of measures of gin or vodka.
© 1995 Frances Bissell. All rights reserved.