1Heat oven to 350°F. Line bottom and sides of 13x9-inch pan with foil, leaving foil overhanging at 2 opposite sides of pan; spray foil with cooking spray.
2In small bowl, mix flour, cornstarch and salt; set aside. In large bowl, beat butter, powdered sugar and granulated sugar with electric mixer on low speed until combined. Beat on medium speed until light and fluffy. On low speed, gradually beat in flour mixture. Stir in cherries. Press in pan.
3Bake 30 to 35 minutes or until lightly browned. Cool completely in pan on cooling rack, about 30 minutes.
4In small microwavable bowl, microwave chocolate chips uncovered on High 30 to 60 seconds, stirring once, until softened and chips can be stirred smooth. Using a fork, drizzle chocolate over bars. Let stand until firm, about 2 hours. Use foil to lift out of pan. Cut into 6 rows by 4 rows.