<ol><li>Into a large bowl, sift together 1 cup of the confectioners sugar, the cocoa powder.
</li><li>Stir in the rum and corn syrup.
</li><li>Stir in the vanilla wafers and walnuts, and mix well.
</li><li>Place in the refrigerator to firm up slightly, about 30 minutes.</li><li>Place the remaining 1/2 cup confectioners sugar in a shallow bowl or dish.</li><li>Using a tablespoon, scoop out portions of the chocolate mixture and press into 1-inch balls. Using your hands, roll the balls in the confectioners sugar, coating evenly.
</li><li>Place on a baking sheet, cover with plastic wrap and refrigerate overnight. Store in an airtight container in the refrigerator for up to 2 weeks, placing waxed paper between the layers to prevent sticking.</li></ol>