Bring butter, sugar, water and cocoa to the boil, always stirring. Set aside 1/2 glass of the thickened mass. Let the rest cool in the pot.
Pour in the desiccated coconut, gradually adding the eggs, flour and baking powder while stirring. Spread the dough on a greased baking sheet and bake with top / bottom heat at 200 ° C for about 20 - 25 minutes.
After baking, distribute the set aside evenly on the still hot cake and sprinkle with a little desiccated coconut.