Boil the milk and sugar in a pan, take 5 tbsp milk in a bowl, add custard powder and cocoa powder, make a slurry without lumps.

As the milk comes to boil, add slurry and stir it well, it becomes thick and boil comes, off the gas. Let it cool the mixture, then grind with a blender.

As it blends properly, serve in a glass with ice and enjoy your cold coco.