Combine the vanilla wafer crumbs, chopped pecans, 1 cup of the confectioners' sugar, and the cocoa. Combine the bourbon and corn syrup and stir into the dry mixture. When thoroughly blended, cover and refrigerate the dough for 1 hour or more. Sift the remaining confectioners' sugar onto a large piece of waxed paper. Take 1 tablespoon of the dough, shape it into a ball, and roll it in the sugar. Repeat until all the dough is used. Store them, covered, in the refrigerator.