Add the flour, sugar and salt to a food processor and pulse just until combined. In a small bowl, whisk mix together the egg, vinegar and water. Add the cold butter pieces into the food processor and pulse until small coarse crumbs remain. Sprinkle the water/egg mixture over the flour and pulse again until the dough comes together.
Remove the dough with your hands, divide it into two equal pieces and wrap them in plastic wrap. Refrigerate the dough for 30 minutes.
After 30 minutes, preheat the oven to 400 degrees F.
Place the blueberries in a large bowl. In a smaller bowl, whisk together the sugar, cornstarch, cinnamon and salt. Sprinkle it over the blueberries and toss them well.
Roll one ball of the dough out on a floured surface into a large rectangle, about 12 inches by 16 inches. (The baking sheet I used was 10 inches by 15 inches – I would not use one much larger for this recipe.) Gently transfer the dough to the sheet and press it into the pan. Add the blueberries on top of the crust.
Use the remaining dough to create a crust on top. You can roll it out and make one large top crust (make sure you cut a few slits in the top), you can make a lattice- like crust as I did or you can make a super fancy one!
Once the pie is ready to go, brush the top crust with the egg wash mixture and cover it with the coarse sugar. Place the pie in the oven and reduce the heat to 375 degrees F. Bake for 50 to 60 minutes, until the crust is golden and the blueberries are bubbly.
Let it cool for a few minutes before slicing. The good news is that it will stay together much nicer than triangular slices! Serve with LOTS of ice cream. :)