Coarsely chop the cake and pulse in a food processor until well mushed (you could also grate it on the coarse side of a box grater). Add the melted 72 per cent chocolate and rum, brandy or orange juice and pulse to combine.
Tip into a small bowl, cover with plastic wrap and refrigerate for about an hour or until fi rm enough to roll.
Roll heaped teaspoonfuls of the mixture into balls, put on a tray lined with baking paper and refrigerate for another hour.
To decorate, dip the chilled truffles in the melted 50 per cent dark chocolate. You will need to reheat the chocolate as you go to ensure it stays warm enough to thinly coat the truffles.
Return the truffles to the lined tray and put back in the fridge until firm. Top with the decorations or edible dust, if using. Store in an airtight container in the fridge for up to 3 weeks.
