Bring the cream to the boil in a small pan. Remove from the heat and stir in the chocolate until it has melted. Stir in the liqueur and pour into a bowl. Cool, then chill until firm, about 4 hrs, or overnight.
Sprinkle a sheet of greaseproof paper with icing sugar and another with cocoa powder. Take a teaspoon and scoop nuggets of truffle mix out of the bowl and onto either the paper with cocoa powder or icing sugar. Use two teaspoons to coat the nuggets then transfer them to paper sweet cases. Pack into paper sweet cases in boxes and chill. Store for up to 2 weeks.
With a different liqueurIf you don't fancy Tia Maria you could use Kahlua, Cointreau or Frangelica, a delicious hazelnut liqueur