In a pan, boil together the sugar, water and zest of the lemon and grapefruit, which you have removed with a potato peeler. Cool.
Squeeze the juice from the fruit and add to the sugar mixture. Cool and chill till just frozen.
When just frozen whisk in a liquidiser with the puréed stem ginger. Re-freeze till very firm.
© 1984 All rights reserved. Published by Jon Croft.