1. Whip together room temperature butter and icing sugar.
2. Add rum essence, jam and cacao. Mix well together.
3. Mix in the cake crumbs and form by hand medium size balls on a piece of baking paper.
4. Leave the balls in the fridge for at least an hour before dipping them in melted chocolate and decorating with sprinkles.
5. Store in a refrigerator in a tight box.
