1.Combine apricots and liqueur in a small bowl, stand for 30 minutes.
2.Stir chocolate in a medium heatproof bowl over a medium saucepan of simmering water until smooth (don’t let water touch base of bowl). Combine chocolate and cake crumbs in a medium bowl, stir in apricot mixture. Refrigerate until firm.
3.Roll rounded teaspoons of mixture into balls, place, in a single layer, on a baking-paper-lined tray. Refrigerate for 4 hours or until firm.
4.Just before serving, bring the truffles to room temperature and roll in sifted cocoa powder.