Remove 1 cake piece from pan, using wide spatula; place on serving plate. Spread 3/4 cup caramel mixture over cake piece. Top with second cake piece; spread with 3/4 cup caramel mixture. Top with third cake piece. Frost sides and top of cake with remaining caramel mixture. Sprinkle reserved whole cashews over top of cake. Cover; refrigerate about 1 hour or until ready to serve. Store covered in refrigerator.