Thoroughly combine 1 crushed vanilla wafer crumbs, chopped pecans, 1 cup confectioners' sugar, and the cocoa. In a separate bowl, blend the bourbon and corn syrup. Stir this bourbon mixture into the dry mixture; blend well. Cover and chill for at least a few hours. Sift about 1/2 to 1 cup of confectioners' sugar on a cookie sheet. Shape small bits of the dough into balls and roll them in the confectioners'. Store in refrigerator in tightly covered containers. Make these a few days in advance for best flavor, and roll in confectioners' sugar again before serving, if desired. These can also be frozen for longer storage.