1. Melt chocolate, butter in 2-quart Sauce Pan over medium-low heat; add egg yolks, rum; beat with wooden spoon or plastic whisk until well-blended; pour into bowl; refrigerate 1 hour or until firm enough to handle.
2. Shape mixture into thirty-six 1-inch balls (about 1 teaspoon each); roll in cocoa; refrigerate several hours or until serving time.
Makes 3 dozen