Crust: Preheat oven to 400°. In medium bowl, mix flours (and optional butter powder) and cut in shortening until it resembles coarse crumbs. In separate bowl, beat together other ingredients and then stir into flour mixture. Mix just until it is incorporated. Form dough into disk, wrap in plastic wrap and chill. Roll out about 1/3 of dough between 2 sheets of plastic wrap and line 9-inch pie dish.
Filling: Thaw frozen raspberries, drain and save juice. Add enough of the juice from cherries to make 1 cup liquid; set aside. In medium saucepan, mix sugar, cornstarch and salt. Stir in 1 cup of juice. Add cherries and cook over medium heat until thick and clear. Cook 1 more minute. Remove from heat and very gently fold in raspberries.
Pour mixture into pastry-lined pie dish. Add top crust, seal edges, moisten top with warm milk and sprinkle with sugar. Cut steam vents in top crust. (This pie is especially pretty with lattice top.) Bake at 400° on bottom shelf 10 minutes. Reduce oven to 350° and continue to bake about 35 minutes or until top is golden brown.