Prepare the pie crust. Combine 4 ½ cups flour, 4 tsp granulated sugar, 1 tsp Kosher salt, and 1 tsp ground cinnamon in the bowl of a food processor fitted with blade attachment. Pulse to combine. Add 1 cup cold cubed butter 14 Tbsp cold cubed shortening, then pulse until pea-sized pieces form.
Add the ice water. Add 6 Tbsp ice water and pulse. Add an additional tablespoon of water until the dough begins to form. 7-8 Tbsp is usually perfect for this recipe, but humidity and temperature can affect how much water is needed. The dough should hold together completely as one ball with no visible clumps.
Chill the pie dough. Remove the dough and separate into two equal sized round disks. Wrap each in plastic wrap, then chill for at least 30 minutes. To speed up the process, place in a freezer for 10-15 minutes.
Note: If pie dough is chilled for an extended period of time, it will be too firm to roll out. Simply leave at room temperature for 5-10 minutes to soften, if needed.
Prepare the bottom crust. Tip: Roll out the dough on a lightly floured piece of plastic wrap to make for easier cleanup! Working with one disk of dough, roll out to fit a 9x2” pie dish. The pie dough should be about 12-inches round (or about 3-inches larger than the pie plate). Carefully roll the pie dough around the rolling pin, then transfer to a pie plate and unroll. Trim excess dough, if needed, so that no more than 2-inches hang over the size. Refrigerate while you make the filling (or up to 8 hrs in advance).
Prepare the blueberry pie filling. Combine 5 ½ cups frozen blueberries, a scant ½ cup granulated sugar, 4 ½ Tbsp all-purpose flour, the zest (about 1 heaping tsp) and juice of 1 lemon (about 2-3 Tbsp), 1 tsp ground cinnamon, and ½ tsp Kosher salt in a large mixing bowl. Stir to thoroughly mix, then pour into the prepared pie crust. The filling should look moist, not floury and dry! Filling can be made up to 1 day in advance.
Prepare the top crust. Roll out the second disk of dough on a lightly floured surface to a similar size and thickness as the first. Cut into strips about ¾” - 1” thick. You’ll need 12 strips total.
Make the lattice top. Place 6 of the strips on top of the prepared pie, leaving an equal amount of space between each. Carefully fold back every other strip, then place a strip of pie crust perpendicular on top. Fold back down the strips of dough, then repeat with the alternate set of parallel strips until the entire pie is covered.
Trim the pie dough. Tuck any excess dough from the strips into the sides of the pie or underneath the bottom pie crust, which should be folded on top to seal. Crimp with your fingers or flute the edges.
Chill for 30 minutes. Refrigerate for 30 minutes, then preheat an oven to 375F.
Brush on the egg wash. Combine 1 large egg yolk and 1 Tbsp heavy cream (or water) in a small bowl, then whisk well. Use a silicone pastry brush to brush the entire pie crust with egg wash.
Bake the pie. Place the prepared blueberry pie on a parchment or aluminum-foil lined rimmed baking sheet. Bake in a preheated oven for 50-60 minutes, or until the top is golden brown and the blueberry filling is bubbling.
Cool, then serve. Blueberry pie can be served warm or at room temperature. Allow the pie to cool for at least 30 minutes before slicing, or 3 hours if serving at room temperature. Serve with a generous scoop of coffee ice cream.