Preheat your oven to 425°F (220°C) and place a baking sheet on the middle rack.
Remove one disk of dough from the refrigerator and let it sit at room temperature for about 5 minutes to soften slightly.
On a lightly floured surface, roll the dough into a 12-inch circle about ⅛-inch thick. Carefully transfer the dough to a 9-inch pie plate.
Pour the fruit filling into the pie crust, making sure to include all the juices. Dot the top of the filling with the small pieces of butter.
Roll out the second disk of dough to the same thickness. You can either place it whole on top of the pie or cut it into strips for a lattice top.
If using a whole top crust, cut a few slits in the center to allow steam to escape. If making a lattice, weave the strips over and under each other.
Trim the excess dough from the edges and crimp or flute as desired.
Beat the egg with 1 tablespoon of water and brush this egg wash over the top crust. Sprinkle with the coarse sugar.
Place the pie on the preheated baking sheet and bake for 20 minutes at 425°F.
Reduce the oven temperature to 375°F (190°C) and continue baking for 30-40 minutes more, until the crust is golden brown and the filling is bubbling.
Allow the pie to cool on a wire rack for at least 3 hours before slicing to let the filling set.