In a large bowl, cream butter and confectioners' sugar until light and fluffy. Beat in vanilla. Combine flour, cornstarch and salt; gradually add to creamed mixture and mix well. Fold in butterscotch chips and toffee bits. Cover and refrigerate 1 hour or until easy to handle.
Preheat oven to 350°. On a lightly floured surface, roll out dough to 1/4-in. thickness. Cut with a floured 2-in. fluted round cookie cutter. Place 1 in. apart on ungreased baking sheet.
Bake 10-12 minutes or until lightly browned. Remove to wire racks.