Combine flour, cornstarch, and sugar in bowl or food processor. Add butter and cut in with pastry blender or process until mixture is crumbly. Press into 9-inch pie plate. Bake at 350 degrees F for 20 minutes, just until golden.
Cook plums and water in skillet over medium heat until juice thickens slightly. Remove from heat. In small bowl, combine remaining flour and sugar with baking powder and egg and enough juice from plums to form smooth batter. Stir into plums until evenly coated. Pour into crust. Bake at 375 degrees F for 20 to 25 minutes. Cool. Cut into 8 pieces. May be garnished with a sprinkle of powdered sugar or a dollop of whipped cream.
Date: August 14, 2002