1. Preheat oven to 425°. Combine first 6 ingredients in a large bowl, stirring until well blended. Let stand 15 minutes.
2. Meanwhile, place 1 piecrust in a shallow 9-inch pie plate; trim edges. Cut three-fourths of remaining piecrust into strips. Cut remaining one-fourth piecrust with a 2-inch star cutter.
3. Spoon cherry mixture into pie plate. Arrange pastry strips and stars on top of filling. Brush pastry with beaten egg.
4. Bake pie, on a foil-lined baking sheet, 15 minutes. Reduce heat to 350°; bake 55 minutes or until filling is bubbly and crust is browned. (Shield edges with aluminum foil, if necessary, to prevent excessive browning.)