Preheat oven to 325 degrees F.
Spread the pecans on a cookie sheet, and place in the oven for 3 minutes. For even toasting, turn the tray, front to back. Toss the nuts with a metal spatula and bake for another 3 minutes. You'll know they're done when they give off their fragrant aroma, and be sure to check them so they don't become overbaked or charred.
In a food processor, chop the vanilla wafers into crumbs. Add the pecans and process just until they are finely chopped. In a medium bowl, mix together the crumb-pecan mixture, 1/4 cup of the cocoa, and 1/4 cup of the confectioners' sugar. Add the corn syrup and bourbon. Mix thoroughly. Sift the remaining 1/4 cup cocoa and 1/4 cup confectioners' sugar onto a large plate. Form the crumb mixture into 3/4-inch balls and roll them through the cocoa-sugar to coat. Store in a sealed container for up to 5 days. If necessary, touch them up with a light dusting of the remaining confectioners' sugar.