How to Make It
Prepare the Filling: Combine sugar, water, butter, cornstarch, and cinnamon in a large saucepan. Whisk over medium-high heat until butter is melted and all of the ingredients are incorporated. Allow mixture to come to a simmer, and let it bubble until thickened, whisking occasionally and until the syrup is thick enough to follow the whisk, about 7 minutes. Remove pan from heat and allow syrup to cool. While the syrup cools, make the dough for the crust.
Prepare the Crust: Combine flour, sugar, and salt in the bowl of a food processor, pulse to combine. Scatter the very cold cubes of butter and shortening over the dry ingredients. Pulse the food processor a few times until the butter and shortening are incorporated into the flour.
In another bowl, whisk together the egg, water and vinegar.
Transfer the contents of the food processor into a large mixing bowl and slowly add the wet ingredients while mixing the dough with your hands. Do not knead the dough, but mix with your hands until the dough sticks to itself and comes together. The dough should be soft and pliable.
Assemble the Pie: Preheat the oven to 425°F. Add blueberries, lemon juice and lemon zest to the cooled syrup and use a spatula to coat the berries.
Divide the dough into two equal halves. Use one half to fill a greased pie plate, making sure to distribute the dough evenly with your hands.
On a well floured surface (this dough is slightly sticky), roll out the other half of the dough into a circle about 1/4-inch thick.
Pour the blueberries and syrup into the dough lined pie plate.
Take the rolled out dough and place it on top of the pie. Follow the perimeter of the pie plate with a knife and cut the overhanging dough. Press the two dough surfaces together making a smooth and unified rim. Crimp the edges with your fingers or with a fork.
Use a pairing knife to make three slits on the surface of the top crust. Place the pie on a baking sheet and bake for 20 minutes. Reduce the oven temperature to 350°F and bake for an additional 30 minutes. Tent the surface with aluminum foil if the crust is browning too quickly. Allow pie to cool completely before cutting.