(1) Mix the cocoa and vegan sugar together.
(2) Dissolve the cornstarch (cornflour) in the water and combine with the cocoa-vegan sugar mixture in a medium-sized saucepan. Stir this until it is a smooth paste.
(3) Begin heating this mixture, continuously stirring it with a whisk. Gradually pour in the soy milk. Continue stirring as you bring it to a simmer.
(4) Simmer, stirring often, for about 10 minutes. The cocoa is ready when it thickens and is glossy and smooth.