Lightly grease 2 x 8inch/20cm heart shaped or round tins
In a large mixing bowl cream the butter with the sugar until very light and fluffy.
Gradually add the eggs and mix in the flour and cocoa powder
Pour the mixture into the prepared cake tins and bake for 20-25 minutes or until the cake is well set-A skewer inserted into the centre of the cake should come away spotlessly clean and dry. When the cake is cooked take it out of the oven and allow it to cool in the tin as it will still be quite soft at this stage.
Ideally you should have the cake made the day before you require it.
Cream the butter and the icing sugar together until light and fluffy.
Add in the melted chocolate the boiling water and mix well.
Use as required.
Divide the butter icing between the middle and the top of the cake
Decorate with some extra melted chocolate or grated chocolate shavings.