Preheat the oven to 180°C and line a 12-hole (2 tablespoon capacity) flat-based cupcake or patty pan with paper cases.
Dissolve the coffee in 1 tablespoon of hot water in a small jug and stir in the butter.
Using an electric hand mixer, beat the egg and sugar in a medium-sized bowl until pale and thick; sift the flours together over the egg mixture and using a large metal spoon, gently fold in until just combined; gently stir in the coffee mixture and the grated chocolate.
Half fill each paper case with the mixture and bake for 15-18 minutes or until a skewer inserted into the centre of one of the cupcakes comes out clean.
Leave the cupcakes standing in the pan for 10 minutes, then transfer them to a wire rack to cool.
Using an electric mixer, beat the cream until it is thick; sift the drinking chocolate and cocoa over the cream and fold it through the cream to create a marbled effect; spoon the cream mixture over the cupcakes, dust with extra cocoa and top each cupcake with a chocolate-coated coffee bean.