To make the crust: Place the flour, salt, sugar and lemon zest into the bowl of a food processor fitted with a metal blade. Pulse for 10 seconds. Add the shortening and margarine or butter and process until the mixture looks mostly like sand, but still has some ¼ to ½ inch piece of fat. Scoop up the tablespoons of ice water from the glass and add to the bowl. Mix just until the dough starts to come together, but mostly looks like clumps of dough.
Gather the dough into a ball and break off a little more than 1/3 (almost 40%) of the dough. Wrap both pieces of dough separately in plastic and flatten. Freeze for 1 hour or overnight, if you have the time.
Preheat the oven to 350ºF. Place an oven rack on the lowest shelf. You will need an 8 or 9-inch pie plate.
Take the smaller piece of chilled dough and place it on a piece of parchment sprinkled generously with flour. Cover with a second piece of parchment and roll out to about 9 inches wide by 12 inches long and 1/4-inch thick. Use a knife or fluted pastry wheel to cut the dough into long strips, about ¾ -inch wide. You should have at least 8 strips. If you have a long fat blade metal spatula, you can lift and separate the strips from each other. This makes it easier to move them to the pie. Slide the parchment onto a cookie sheet and carefully place in the freezer.
Meanwhile, remove the larger piece of dough from the freezer and place on a piece of parchment sprinkled with flour. Sprinkle the top of the dough with some flour and cover with a piece of parchment. Roll on top of the parchment to roll the dough into a circle about 1 inch larger than your pie pan. Peel back the top parchment a few times and sprinkle flour on the dough as you roll.
Remove the top parchment. Place your hand under the parchment, lift the dough and turn it into the pie pan. Remove the parchment. Use your hands to gently press the dough into the corners. Fill any holes with extra dough Use a knife to trim the dough that is hanging over the sides of the pan.
To make the filling, in a medium bowl, combine 3 cups of the blueberries with the sugar, cinnamon, salt and cornstarch. Use a potato masher to combine the ingredients together. Some blueberries will remain whole. Add the remaining cup of blueberries and stir in. Dump the filling into the crust and spread evenly.
To assemble the lattice: Place half the dough strips (4-5) horizontally across the pie, about 1 1/2 inches apart. Fold the first and third strips back over themselves in half. Place another strip vertically across the unfolded strips next to the folded strips and over the strips that lay across the pie. #69 Unfold the folded strips over the new strip. Now fold back the strips that were not folded before, the second, and fourth strips. Add another vertical strip next to those folds, 1 ½ inches from the other, over the unfolded strips and then unfold the folded ones. Repeat for the other side of the pie. Alternating the strips that are bent back as you add the next strip until you have covered the pie. Trim the edges of the pie plate and press to seal the edges.
Use a pastry brush to brush the beaten egg white all over the top of the crust and lattice. Sprinkle the teaspoon sugar all over the top. Place on a jelly roll pan and put on the bottom rack in the oven. Bake 1 hour, or until the top of the crust starts to brown and the blueberries look bubbly.