Chop up the dates into small pieces and pour over the hot coffee (making sure all of the dates are covered in liquid). Let the mixture sit for around 20 minutes (until the dates are softened).
When ready, blitz in a food processor until you have a thick, fairly smooth, paste.
Add the cocoa powder and process until everything is well combined. Put the frosting in the fridge until ready to use. The longer you leave it there, the more the flavor enhances, and the texture becomes more "fudge" like.
When ready to assemble, just slather the frosting over the top of the cake. You can leave the cake out on the counter, but if you want a firmer frosting, keep it in the fridge. Enjoy!