Combine Valrhona® Cocoa Powder (2 1/2 teaspoon) and Caster Sugar (4 1/2 tablespoon) together in a pot. Add in the Water (4 tablespoon) into it and stir well.
Gradually pour in Milk (550 milliliter) and Vanilla Extract (1 teaspoon), stir well again. Under medium heat, bring milk mixture to a boil.
Soak the Gelatin Sheet (4) into cold water for a few seconds, squeeze out excess water and drop into milk mixture, stir till gelatin melted. Turn off heat and stir in Nutella® (2 tablespoon), stir well again till melted.
Strain chocolate liquid mixture and pour into serving cups. Chill pudding for at least two to three hours till set.