Preheat oven to 350 degrees.Combine flour, cocoa, baking soda and salt in med. bowl. Beat butter and sugar in lg. bowl of electric mixer on med. speed until light and fluffy. Beat in corn syrup, egg and vanilla until well blended. Gradually beat in flour mixture at low speed until blended. Cover and refrigerate dough until firm, about 15 min. Roll dough into 1 in. balls using about 1 tbs. dough per ball. Place balls 2 in. apart on ungreased cookie sheets. Press lightly with fingers to flatten slightly. Bake until cookies are set, 10 - 12 min. Immediately transfer to wire racks; cool completely. Soften ice cream at room temperature about 10 min. For each ice cream sandwich, place about 1/4 cup (1 small scoop) ice cream on flat side of a cookie; top with another cookie, flat side down. Press gently so that ice cream meets edges of cookies. Immediately roll edges of ice cream in decorations. Wrap in plastic wrap; freeze until ready to serve.