FOR THE filling:

1. Combine cornstarch and water in a small bowl, stirring to dissolve.
2. Put 2 cups of the cherries in a blender and puree.
3. Combine the puree and sugar in a medium saucepan and simmer over medium heat for 30 minutes, stirring often.
4. Reduce the heat to medium-low and while stirring constantly, add the cornstarch slurry.  
5. Bring to a boil while continuing to stir and cook until the mixture becomes translucent and there are no remaining grains of starch.
6. Transfer the filling to a medium bowl and stir in vanilla extract. Allow to cool completely.

FOR THE pie crust:

1. Roll out pie dough according to the recipe on Cup4Cup pie crust mix.
2. Place 1 dough in a pie plate and the other on a sheet pan and refrigerate until cold.
3. Remove the chilled pie crust from refrigerator.
4. Preheat oven to 400°
5. Stir the puree into the whole cherries and pour into the pie shell.
6. Moisten the rim of the pie shell with some of the beaten egg.
7. Cover the filling with top crust and press edges together to seal, creating a raised edge to the crust. Trim away the excess dough.
8. Brush the top crust with beaten egg and sprinkle with sugar if desired.
9. Using a paring knife, cut a few slits in the top crust for steam vents.
10. Place pie on bottom rack of oven and bake for 20 minutes.
11. Lower the heat to 375°, move pie to center rack and bake 20-30 minutes until the crust is golden and the filling is bubbling.
12. Transfer pie to a cooling rack.