for the crust
2 1/2 cups all purpose flour
1 tablespoon sugar
3/4 teaspoon salt
10 tablespoons (1 1/4 sticks) chilled unsalted butter, cut into 1/2-inch pieces
1/3 cup chilled solid vegetable shortening, diced
6 tablespoons (or more) ice water
for the filling
2 cups blueberries, fresh or frozen
2 cups cranberries, fresh or frozen
2 tablespoons lemon juice
3/4 cup sugar
4 tablespoons corn starch
2 tablespoons milk, for egg wash
1 egg yolk, for egg wash
2 tablespoons turbinado sugar
And you will also need: a 9 inch cast iron skillet
Blend flour, sugar and salt in processor. Add butter and shortening and cut in using on/off turns until mixture resembles coarse meal. Add 6 tablespoons ice water and process until moist clumps form, adding more water by teaspoonfuls if dough is dry. Gather into ball, then flatten into a disk. Wrap in plastic and chill 2 hours.
Prepare your filling by combining blueberries, cranberries, lemon juice, sugar and corn starch in a medium bowl, and toss gently to coat.
Preheat to 425F. Spray the cast iron pan with cooking spray. Roll out dough to a roughly 11-12 inch round. Lay out pie crust onto skillet. Press the sides along the side of the pan, but just gently, because you will want to fold this part onto the peach mixture. Combine the milk and egg yolk to create an egg wash.
Dump the cran-blueberry mixture onto the middle of the pie crust. Fold the edges of the pie crust onto the mixture; it won’t cover all of it and you should see some of the berry mixture in the middle. Use some of the egg was to glue the fold together and then brush the top crust with egg was as well. Sprinkle with turbinado sugar.
Bake in oven for 35-40 minutes, or until crust is browned and cran-blueberry mixture is bubbly. Remove from oven and allow to sit for 20 minutes or so before serving. Serve warm.