Put the chocolate pieces in a heatproof bowl and set over a saucepan of hot water. Stir until melted.
Spoon 12 spoonfuls of the melted chocolate on to a baking sheet lined with baking parchment and allow to spread into about 7 cm (3 inch) discs, then refrigerate for 30 minutes until set.
Whip the coconut cream in a bowl until thick. Layer 3 chocolate discs on each of 4 serving plates with the coconut cream, mint leaves and raspberries.
Mix the cocoa and icing sugar together, then dredge over the chocolate stacks to serve.