Stir sugar and 150ml water in a small saucepan over medium heat until sugar dissolves, then bring to the simmer. Remove from heat, then chill completely in refrigerator. Purée prickly pear, lemon juice and 150ml sugar syrup in a food processor until smooth, strain through a sieve into a tray and freeze, stirring occasionally with a fork to break up ice crystals, until firm and frozen (10-12 hours). Makes about 700ml.
For mandarin granita, blend mandarin juice, sugar and lemon juice in a blender until sugar dissolves, strain through a sieve into a tray and freeze, stirring occasionally with a fork to break up ice crystals, until firm and frozen (10-12 hours). Makes about 700ml.
For vanilla ice-cream, bring milk, cream, vanilla and 25gm sugar to the boil in a saucepan over medium-high heat. Whisk yolks and remaining sugar in a heatproof bowl until sugar dissolves, add milk mixture and whisk to combine. Return mixture to pan and stir continuously until mixture thickly coats a wooden spoon (5-6 minutes). Remove from heat, stir for a few minutes, then strain through a sieve and refrigerate until chilled. Freeze in an ice-cream machine, then freeze until required. Makes about 1 litre.
To serve, mash granita with a fork to remove any lumps (a fine, even texture is most desirable). Pile prickly pear granita and mandarin granita into frozen coupes or glasses, top with vanilla ice-cream and serve.
This recipe is from the September 2012 issue of Australian Gourmet Traveller.