Sift flour, baking powder and salt twice. Transfer to a mixing bowl.
Add cocoa powder, oil, egg, yogurt and vanilla essence. Stir to mix.
Boil ½ cup water and add to the remaining ingredients, Beat well to mix to a smooth batter.
Pour into greased and floured cake tin and bake for 45 minutes or until done in a medium oven.
Cool and remove from cake tin.
Place on serving platter and drench with the syrup of hot water, cocoa powder and castor sugar. Part of the water can be substituted with alcohol if desired.
Heat butter with 2 tablespoons of water. Add cocoa powder and icing sugar. Add as much water as necessary to get a thick pouring consistency. Pour over cake and leave to set.
The remaining icing can be used to decorate the cake. The icing can be thickened to piping consistency by adding a little cocoa powder and icing sugar.