Make truffles. Combine cream and dark chocolate in small saucepan, stir over low heat until smooth. Transfer mixture to small bowl, cover, refrigerate 3 hours. Roll ½ teaspoonfuls of mixture into balls, place on tray. Roll balls in Peppermint Crisp, return to tray. Refrigerate truffles until firm.

Stand eight 10cm lengths of cleaned PVC pipe on tray, line each pipe with baking paper.

Process biscuits and Peppermint Crisp until fine. Add butter, process until combined. Divide mixture among pipes, using end of wooden spoon, press mixture down evenly. Refrigerate 30 minutes.

Make filling by sprinkling gelatine over the water in small heatproof jug, stand jug in small saucepan of simmering water. Stir until gelatine dissolves. Cool 5 minutes.

Beat cream cheese and sugar in medium bowl with electric mixer until smooth. Stir in gelatine mixture and liqueur, fold in cream. Divide filling among pipes, refrigerate overnight.

Remove pipes and paper from cheesecakes. Serve topped with truffles and mint leaves, if desired.