Pre-heat oven to 180°C (160°C fan-forced). Line the base and sides of 2 x 20cm deep cake pans. Place butter and sugar into the bowl of an electric mixer and beat until pale and creamy. Add eggs one at a time, mixing until well incorporated. Add in the vanilla.
Slowly add flour and baking powder alternately with the milk, until well combined and the batter is smooth.
Divide batter between prepared pans and bake for 45 minutes, or until an inserted skewer comes out clean. Cool for 10 minutes in pans before removing to a cooling rack. Once cooled completely, refrigerate covered until ready to decorate.
For icing, combine the icing sugar and cocoa in a large mixing bowl. Make a well and add the butter. Pour in the boiling water, allowing it to melt the butter slightly. Mix well until smooth.
To decorate, trim the top off one of the cakes, so it has a flat surface. Spread the outer edges with chocolate icing. Working quickly, then sprinkle with the coconut. Place onto a cooling rack to set. Then with the second cake, cover the top and sides with icing, and sprinkle well with coconut. Allow to set.
To assemble, place the first cake onto a serving plate, spread the top with jam and then spread or pipe on the whipped cream. Top with the second cake and serve.