Combine cream and 200g chocolate in a heatproof, microwave-safe bowl. Microwave, uncovered, on medium (50%) for 2 to 3 minutes, stirring every minute with a metal spoon, or until melted and smooth. Stir in liqueur. Set aside for 10 minutes to cool. Stir through Peppermint Crisp. Cover and refrigerate for 3 to 4 hours or until firm.
Line a tray with baking paper. Using 2 teaspoons chocolate mixture at a time, roll into balls. Place on tray. Freeze until firm.
Place remaining dark chocolate in a heatproof, microwave-safe bowl. Microwave, uncovered, on medium (50%) for 2 to 3 minutes, stirring every minute with a metal spoon, or until melted and smooth. Using a fork, dip truffles in melted chocolate, shaking off excess. Return truffles to tray. Refrigerate until set.
Place white chocolate in a heatproof, microwave-safe bowl. Microwave, uncovered, on medium (50%) for 1 minute, stirring after 30 seconds with a metal spoon, or until melted and smooth. Spoon chocolate into a snap-lock bag. Snip off one corner and pipe chocolate over truffles. Refrigerate until set.