1) In a saucepan, combine water, sugar and cocoa powder. Cook over medium heat until mixture starts to bubble. Cook and whisk mixture till it slightly thickens. Remove from heat and let it cool.
2) Pour mixture into a large shallow dish or container. The dish should be large enough to go into your freezer and also, the shallower the container, the quicker the granita will freeze.
3) Cover with lid or plastic foil, put in freezer. Every 30 mins, take container out of freezer and scrape the ice with a fork. Return container to freezer. Repeat this step for 2 hours or until the mixture has turned into small-crystal ice flakes.
4) When ready to serve, scrape again with fork to loosen the granita, and spoon into serving bowls.