Mix two cups water with cornstarch. Set aside. Bring coconut milk, sugar and remaining water to a rolling boil on high heat. Pour cornstarch mixture into boiling coconut milk and cook till mixture thickens, blending with a whip.
When mixture is smooth and thick pour into a clean baking tray. Cool to room temperature, then chill until cold.
Once completely chilled solid, cut into 1-inch squares or larger. Serve on ti leaf lined trays