Cream together butter and sugar until fluffy. Gradually add eggs, beating well after each addition. Sieve flour and cocoa powder. Fold into the mixture. Pour the mixture in the prepared tin and level the top. Bake in a preheated oven, 350F, for 40 minutes or until springy to the touch. Leave to cool for 5 minutes in the tin, and then turn out to a wire rack to cool.
Place chocolate, milk and butter in a heatproof bowl set over a pan of hot water. Stir until the chocolate has melted. Add the icing sugar beat until smooth. Leave to cool until thick enough to spread, and then spread it all over the cake. Sprinkle with the shredded coconut and allow the icing to set.
Cut a V – shape wedge from the top of the cake. Put the cream in a piping bag fitted with a star nozzle. Pipe the cream down the center of the wedge and replace the wedge of the cake on top of the cream. Pipe another line of cream down either side of the wedge of cake. Serve.