In a food processor combine cake, pecans and sugar; pulse several times to mix well. Add bourbon, a little at a time, just until moistened and it forms a soft pliable dough. Turn out dough onto work surface lightly dusted with confectioners' sugar. Dust your hands lightly with confectioners' sugar, pull off walnut-sized pieces and roll them between your palms to form compact balls. Roll them in cocoa.