• In a large bowl, stir together the flour and salt.
  2 cups all-purpose flour, ½ teaspoon kosher salt
• Cut or grate the butter into small pieces into the flour mixture.
  ⅔ cup cold butter
• Use a pastry blender or sturdy fork to combine the butter and flour until the mixture becomes crumbly.
• Mix the ice water into the bowl a tablespoon at a time until the mixture begins to form a dough.
  6-7 tablespoons ice water
• Separate the dough into two equal portions. Form the dough portions into discs, then wrap them in plastic wrap and refrigerate for at least 30-60 minutes.
• Preheat your oven to 350 °F (177 °C)
• Remove one disc of the pie crust and place it onto a well-floured surface. Roll the dough out into a 10-11" square, roughly ⅛ inch thick.
  
• Carefully drape the rolled dough over an 8x8 square cake pan or casserole dish, then press the dough into the bottom and sides of the pan. Use a knife to cut off any excess dough hanging over the edges of the pan.
• Use a fork to prick the dough all over in order to allow trapped air to escape from under the crust as it bakes. Line the crust with aluminum foil and fill with pie weights, uncooked rice, or beans, then bake for 10-12 minutes.
  

For the filling:

• Add the blueberries, sugar, lemon zest, and cornstarch to a bowl. Toss with a spoon or fork to coat the berries evenly.
  6 cups wild blueberries, ⅔ cup sugar, Zest of 1 lemon, ¼ cup cornstarch
  
• Remove the par-baked pie crust from the oven and discard the pie weights. Spoon the blueberry filling mixture into the crust. Spread the filling evenly using a spoon.
• Remove the other pie crust disk from your refrigerator and, again, roll it into a square over a well-floured surface.
• Using a sharp knife or pastry cutter, slice the dough into long strips, about ½-¾ inch wide.
• Arrange the pastry strips over the blueberry pie filling and weave them into a lattice topping. Use a knife to cut off any over-hanging dough. Add a braid around the edges or create a scalloped edge if desired.
  
• Beat the egg and cream or water together, then gently brush the mixture over the top of the pie crust. Generously sprinkle the additional sugar over top.
  1 egg, Splash of heavy cream or water, 2 tablespoons sugar
  
• Bake for 40-50 minutes or until the crust is golden brown and the filling is bubbly. Cut into squares and serve