Melt the dark chocolate in a Bain Marie (double boiler) and leave to cool for a while.
In the meantime, again using a processor (or whisk) beat the butter until light and fluffy.
Sift the icing sugar and cocoa together, then add them to the butter, continuing to mix until everything is nicely combined.
With the mixer still running, slowly pour in the chocolate.
Finally, gradually add the brewed coffee a little at a time, just until you reach a spreadable consistency.
Place one of the cakes upside and down and spread around a third of the frosting over the flat part.
Place the second cake on top (flat part down) and then use the remaining frosting to cover the whole cake.
Decorate with anything you fancy (I used tiny brown balls and cream-coloured sprinkles) and then leave the frosting to set before slicing the cake. Enjoy!