Melt a good (70% cocoa) slab of dark chocolate over a bain-marie. At this stage you can add chopped nuts, cherries, orange zest and a little liqueur if you like. Remove the melted chocolate from the stove and leave to cool until firm enough to roll in your fingers. Place a few spoons of good-quality cocoa powder on a baking tray and shake the tray to distribute the cocoa evenly. Wet your hands and roll the chocolate into small balls. Drop the balls into the cocoa powder and shake to coat well. Place in a colander and shake off the excess cocoa. Keep in a sealed container in the fridge until ready to serve.