A simple all-in-one chocolate orange cake ... line two 20cm/8in loose-based sandwich tins with baking paper. Mix 50g/1¾oz of the cocoa powder with the just-boiled water to make a smooth, thick ...
Secondly, it should have a shiny exterior (unless coated in cocoa powder, etc), free of blemishes or white "bloom" (a sign that the chocolate was not treated properly during production or storage).