Lemon and lime granita

Method

1. Peel the zest from the lemons and limes with a potato peeler and chop roughly. Put the sugar, 150ml water and zest into a pan and stir over a gentle heat, until the mixture comes to a simmer and the sugar dissolves. Remove from the heat and cool.
2. Squeeze the juice from the lemons and limes and stir into the sugar syrup. Strain the mixture into a shallow freezerproof container with a lid, cover, and freeze until the mixture begins to freeze at the edges – about 2 hours.
3. Scrape all the ice from the sides of the box and break up into smaller crystals with a fork. Re-cover and return to the freezer. Repeat every 30 minutes, until you have a frozen but grainy mixture. Return to the freezer until you are ready to serve.
4. Spoon into tall glass tumblers, decorate with a twist of lemon or lime zest, if you like, and serve.