Mix water, cream, sugar and cocoa in a saucepan on the stove and stir with a whisk.
Bring to a boil and cook for a few minutes; to test if the glaze quality (or nappage) is right dip a spoon into the glaze coating: if it does not slip away you have the right glaze consistency.
Let cool to 60°C and add the hydrated gelatine, then mix with an immersion blender.
Let it chill in the fridge for a few hours.
The pouring temperature of this mirror glaze is about 35°C and it has to be blended with an open head hand blender (e.g. Bamix). The dessert must be frozen and demoulded just before you glaze it to avoid frost formation on the surface.