When well blended, reduce the speed to low and add confectioners' sugar and blend thoroughly. Spread this mixture evenly over brownies. For the glaze, microwave butter and chocolate, until melted and smooth, stirring at 30 second intervals. Let the mixture cool slightly, add in corn syrup, mix well, and spread over the filling. Refrigerate for an hour or until the filling and glaze sets. Lift the foil onto a cutting board; cut the fudge into 6 rows and columns.