Whisk the egg whites in a clean, grease free bowl until just stiff. Add the caster sugar bit by bit and continue whisking until the mixture is really stiff and glossy. Fold in the grated chocolate.
Spoon or pipe the mixture into small fingers or rounds on a lined baking tray. You can place them quite close together as they won't change their shape. Dust with a little cocoa powder and bake for 1 hour until light and crisp on the outside. Turn off the oven and leave to cool for a further hour without opening the oven door.
When you are ready to serve, whisk the cream and coffee until it starts to stiffen. Add the sugar, and keep whisking until it forms soft peaks.
Spread a little of the cream onto half of the meringues and sandwich with one another in an "embrace". Dust with a little more cocoa powder and serve.