Fill a saucepan ¾ with water. Bring it to a boil on a stove and take it off the heat. Add the chocolate pieces to a heatproof bowl and hold it over the water stirring the chocolate so that it melts. As the chocolate starts to melt (pictured above) add the sugar and cocoa powder. Stir till you have a rich chocolate mixture. Remove from the heat, allow it to cool slightly before adding the milk. Stir to combine thoroughly. Once it has cooled completely, give it a quick blitz in the mixer with the ice cubes.