Preheat oven to 350 degrees. Use one pie crust to fill a dry pie plate, fitted to the edges. Roll out the second pie crust and cut out shapes as desired. Set aside.
Spoon in the pie filling. Half blueberry and half cherry. (If you want 3/4 the pie cherry, you will need another can of cherry pie filling.)
Decorate the top of the pie as desired with the second pie crust pieces. Mix an egg yolk with 1 TB of milk and brush on the crust.
Bake pie on a baking sheet for 60 minutes or until the topping is set and the crust has browned.
Check after 30 minutes and cover with foil if crust is turning brown too quickly. Cool for about 1 hour before slicing and serving.
