1. In a small saucepan, heat cream over medium heat until it comes to a simmer. Stir in butter until melted. Remove from heat and stir in chocolate and vanilla until completely melted. Let stand 5 minutes. Stir with a wire whisk until smooth and transfer to a bowl. Let chill until firm, at least 4 hours.
2. Place cocoa in a medium bowl. Using a small spoon, scoop out heaping teaspoonfuls of the chocolate mixture. Working quickly to keep it from melting, roll it between our palms into 1-inch balls. Roll balls in cocoa to coat. Makes 40 balls.To Make These Goodies a Gift::
3. An antique painted box makes a charming presentation for our decadent Rum Balls and Chocolate Truffles. Line the box with a linen napkin to keep the treats from sliding, and place each ball in a mini foil-lined baking cup in gold or silver. (Find them at New York Cake and Baking at 800-942-2539 or www.nycake.com)