In small bowl, sift to combine cornstarch and cocoa .Sifting cocoa and corn starch removes lumps. Add water to form a paste.
In large saucepan over medium heat, stir together soy milk, vanilla, sugar, and cornstarch/cocoa mixture. Cook, stirring constantly, until mixture boils. Continue to cook and stir until mixture thickens
Remove from heat. Pudding will thicken as it cools. Allow to cool five minutes- 10 min. , then chill in refrigerator until completely cool.