Preheat oven to 180°C. Line a 24cm round cake pan with grease proof paper.
Place Dr. Oetker Nona Sponge Cake Chocolate, eggs and water in a mixing bowl. Mix at medium speed for 6 minutes. Add in butter and mix at low speed for 1 minute or until batter is light and fluffy.
Bake at 180°C for 45 minutes. Stand in pan for 10 minutes. Turn out onto a wire rack. Cover with a clean tea towel. Set aside over night.
Sift icing sugar and cocoa into a bowl. Add butter and boiling water. Stir until smooth.
Cut cake into 15 pieces. Place coconut in a dish. With a fork, dip 1 piece of cake in icing, then toss in coconut. Place on a wire rack over a baking tray. Repeat with remaining cake, icing and coconut. Stand for 2 hours or until set. Serve.