Heat the chocolate and cream in a heatproof bowl set over a pan of just simmering water, making sure the bowl does not touch the water. Stir until the chocolate has melted and the mixture is smooth.

Remove from the heat, and mix in the cake crumbs and rum. Leave to cool at room temperature until the mixture is firm enough to roll into balls, about 1 hr – don’t worry if it splits slightly. If you’re short of time, chill the mixture for up to 30 mins, stirring every 10 mins, until firm.

If the mixture splits, stir again until smooth. Put the sprinkles in a shallow dish. Roll teaspoonfuls of the mixture into balls, then roll in the sprinkles to coat. Will keep in a cool, dry place in an airtight container for up to a week.