Combine the cream and butter/margarine in a saucepan and bring to the boil. Break the chocolate into small pieces and add to the hot cream mixture. Stir until the chocolate has melted. Stir in the icing sugar and liqueur. Refrigerate for a couple of hours. Mix the icing sugar with the grated chocolate on a small plate. Shape the truffle into balls and roll them in the chocolate mixture. Store in an airtight container in the refrigerator.
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