Preheat oven to 425 degrees.  Line a cookie sheet with a piece of foil or parchment paper and set aside.

PIE CRUST

1. Add the flour and salt to a large mixing bowl and whisk together.  Using a pastry cutter or two forks, cut in the shortening until it resembles the size of peas.  Add the ice water and mix for a few seconds until the dough comes together.  Transfer the dough to a lightly floured surface and dust with flour if needed.  Pat dough into a round disc.  Cut the dough in half and form each half into a disc.  Wrap in plastic wrap and refrigerate for 30 minutes.

PIE FILLING

1. In a large mixing bowl, whisk together the sugar, lemon juice, lemon zest, flour, cinnamon, and salt .  Add the blueberries and gently mix with a large spoon until the blueberries are evenly coated with the other ingredients.
2. On a well floured surface, roll out one disc of the pie dough into a circle, one inch bigger than the diameter of a 9-inch pie dish.  Fold the dough in half or roll it up over your rolling pin and transfer it to the pie dish, being careful not to stretch the dough.  Stretching the dough will cause it to shrink while baking.  Add the blueberry filling and dot the top of the filling with the butter.
3. Roll out the second disc of dough to a thickness of 1/8 to 3/16 inch thick. I like to roll mine as thin as I can get it without the dough breaking when I form the lattice. Thicker strips of dough are easier to work with, so feel free to roll yours thicker if you want.
4. Arrange rows of strips across the top of the pie. Fold over every other strip halfway up and place another strip of pastry across. Unfold the strips and fold over the other strips. Repeat this process until the lattice is finished.
5. Trim the excess ends of dough strips and pinch the strip ends together with the bottom edge. Brush with the egg wash and sprinkle with granulated or sanding sugar. Tent the edge with tin foil and bake at 425 degrees for 20 minutes then reduce the temperature to 350 degrees and bake an additional 50 minutes or until golden and bubbling. 
6. Allow the pie to cool to lukewarm so that the filling has time to set up. Slice and serve.
7. Refrigerate pie for up to 3 days.