Firstly, in a pan heat the water and sugar until they come to theboil, ensuring that all thesugar is dissolved. Once dissolved, take the pan off the heat and allow thethe syrup to cool. Meanwhile, place the shiso and syrup in a blender andpuree untilsmooth.
Tranfer this mixture into a container and freeze over night. To serve, scrape the desired amount onto a serving dish with a fork.