In a food processor, combine the all-purpose flour, white granulated sugar, and kosher salt.
Pulse the dry ingredients in the food processor quickly until combined.
*“Pulse” just means to switch the food processor on and off really quickly, instead of leaving the food processor running in the “on” position.
Add in your cubed cold salted butter, and pulse again quickly a few times until the flour begins to become incorporated with the butter cubes.
Pour in the extremely cold ice water and pulse the mixture a few more times in the food processor, until the mixture begins to come together and forms a large blob of dough with dots of cold butter mixed in.
Pour the contents out onto a clean work surface, and cut the dough into two pieces.
Form each piece of dough into a dough ball by pressing the dough together with your hands until it forms a compact ball.
*You will have one piece of dough for your bottom crust, and another for your top crust.
Cover the two dough balls individually with plastic wrap, and place them in the fridge to rest for an hour or more.
When your dough balls have rested for an hour in the fridge (or overnight, or if you prefer), remove the first dough ball from the fridge and transfer it onto a lightly floured, clean work surface.
*Save a little extra flour on the side for flouring your rolling pin and adding flour to your dough as you roll it out.
Roll the first dough ball out using a rolling pin into a roughly 12” circular shape that is large enough to fill your pie dish and come up over the sides by about ½”.
*While you roll the dough out to a uniform thickness, make sure to keep to dough lightly floured and moving constantly, so it doesn’t stick to your work surface or rolling pin.
Gently fold the circular pie crust that you have just rolled out in half, and transfer the rolled-out and folded crust to your pie dish.
*Folding the thin dough gently in half at this stage makes it easier to transfer the crust into the pie dish without ripping it.
Unfold the pie crust gently, making sure the crust occupies the full space of the pie dish and comes up the sides, with a slight overhang of dough roughly ½” beyond the outer edges of the pie dish.
*If you rip your dough at all during this process, just take a little extra dough and press it into the hole that you have made--Everything will be fine!
Use a sharp knife or kitchen scissors to carefully cut off any excess dough that hangs more than ½” beyond the edge of the pie dish.
For your egg wash, combine the whole egg with the 1 Tbsp of water and whisk for a minute or two to fully combine.
Use a pastry brush or your clean fingers to gently coat the bottom layer of pie crust that you placed into the pie dish with a very thin layer of the egg wash.
Save the excess egg wash for the top layer of your pie crust that will be added on top of the blueberry pie filling.
Place the pie dish with the bottom layer of crust in the fridge while you prepare the pie filling.