Preparation Stir chocolate in top of double boiler set over simmering water until melted and smooth. Remove from over water. Whisk in 1/2 cup sugar and corn syrup, then the rum. Mix vanilla wafers and walnuts in medium bowl to blend; add chocolate mixture and stir to blend well. Place remaining 1/2 cup sugar in shallow bowl. For each rum ball, roll 1 scant tablespoon chocolate mixture into generous 1-inch ball. Roll balls in sugar to coat evenly. Cover and refrigerate at leas overnight and up to 5 days.
Preparation Stir chocolate in top of double boiler set over simmering water until melted and smooth. Remove from over water. Whisk in 1/2 cup sugar and corn syrup, then the rum. Mix vanilla wafers and walnuts in medium bowl to blend; add chocolate mixture and stir to blend well. Place remaining 1/2 cup sugar in shallow bowl. For each rum ball, roll 1 scant tablespoon chocolate mixture into generous 1-inch ball. Roll balls in sugar to coat evenly. Cover and refrigerate at leas overnight and up to 5 days.