Make 1 quantity basic sponge cake in an 18cm-square cake tin and cool on a wire rack. Cut into 6cm squares. Sift together the icing sugar and cocoa. Mix with the boiling water and melted butter. Using 2 forks to hold the sponge squares, dip in the chocolate icing and roll in desiccated coconut. Allow to set on a wire rack. Makes 9.