Mix together coffee and rum. The original recipe calls for instant coffee (I've also used a shot of espresso). In a separate bowl, melt chocolate and let cool slightly.
Cream butter and icing sugar. Add melted, cooled chocolate, coffee-rum mixture, and vanilla mix well. Chill until firm enough to handle: 3-4 hours.
Drop mixture by teaspoon measures into crumbs (if using) or use a cookie scoop to form balls. Roll in your favourite coating (eg. raspberry powder, hazelnuts, coconut, cocoa powder, dip in melted chocolate).
Place truffles on a plate or baking sheet. Drizzle with melted chocolate (if desired). Chill for 2 hours or until set.
Store in refrigerator in airtight container. Makes 3-4 dozen truffles. Best served chilled!