Assemble the pie: Preheat oven to 375 degrees.
Cut a piece of parchment paper that fits the baking sheet you'll use. Remove one disc of pie dough from the freezer, and gently roll it out on lightly floured parchment paper. (Flour your rolling pin, too). Be gentle, and turn the dough as you go to avoid cracking and sticking. Roll dough out to roughly 11 x 16 inches. Pick up the sheet of parchment paper with the dough and place on the baking sheet. Evenly spread the filling onto the dough, leaving a 1-inch border all the way around. Dot the filling with the butter. Roll out the second dough disc on another piece of parchment (it may need to set out for a few minutes to become pliable) to roughly the same size as the first. Use rolling pin to help transfer this piece over the pie filling. Seal (pinch) the top and bottom crusts together around the edges using your hands. Flute the edges or crimp with a fork. Cut slits into the top of the crust, and brush with a thin coating of egg wash (whisk together the egg and milk). Sprinkle with coarse sugar. Transfer the whole thing to the fridge and let chill for 15 minutes.