Dough. In a large bowl, mix the flour and salt. Add the cubes of butter and the lemon zest. Using your hands, toss the butter to coat each piece of butter with the flour mixture. Pinch the pieces of butter to flatten them a bit. Keep working the mixture for a couple of minutes until the mixture resembles coarse sand with most of the clumps of butter the size of peas and some larger pieces the size of walnuts. Make a well in the middle. Add the Limoncello and the sour cream. Using your hands, scoop the flour from the sides and the bottoms towards the Limoncello/sour cream to hydrate the flour. You may need to knead the dough a couple of times, but do not overwork it. The dough will seem wet and slightly sticky. Gather the dough onto a lightly floured surface and shape into a rectangle using lightly floured hands and a bench scraper.
Using a lightly floured rolling pin, roll the dough out to approximately 8 inches by 10 inches. Using a pastry brush, dust off any excess flour. With the longer side facing you vertically, fold the dough into thirds like a letter (fold the top third down, and the bottom third up). Rotate the dough 90°, roll it out again, and fold it again the same way. Wrap in plastic wrap and refrigerate for at least one hour.
Filling. Pour the berries into a 2 quart size saucepan. Pour the lemon juice over. In a separate bowl, combine the sugar, cornstarch (or Clear Jel) and salt. Pour over the blueberries. Over medium-high heat, stir the mixture and cook until the juices on the bottom start to simmer. Reduce the heat to medium and continue stirring until the mixture thickens, which should take 3-5 minuets. Remove from heat and allow to cool to room temperature before using. (It is best to make it in advance and refrigerate it before assembling the pies.)
Assembly. Preheat oven to 350°F. On a piece of lightly floured parchment paper, roll the dough to a 14 inch by 14 inch square. If the dough becomes too sticky and warm, slide it (use the parchment it is on) onto a baking sheet and put it in the refrigerator for 10 minutes or the freezer for 5 minutes. Cut the dough into 16 squares, each 3½ inches by 3½ inches. Using a metal spatula dipped in flour, release 8 of the 3½ inch squares and place on two baking sheets, four on each sheet. Place the remaining 8 squares in the refrigerator. With a pastry brush, paint a small border of egg wash along the perimeter of the 8 squares. In the center of each square, place a heaping tablespoon of the filling. Remove the remaining squares from the refrigerator and place each on top of the prepared bottoms. Use your fingers to press the edges of the tops into the bottoms. Use a fork to crimp the edges or roll a pastry cutter along the edges. With a toothpick, poke holes to create vents on the top of the pastry. Alternatively, use a knife to make a few decorative slits. Refrigerate or freeze the prepared pies for 10 minutes.
Bake. Remove the pies from the refrigerator or freezer. Egg wash the tops and place in oven. Bake for 18-20 minutes, until the tops are golden brown. (If the filling creeps out of the pastry while baking, use a spoon or small metal spatula to insert it back in when the pies come out of the oven.)
Glaze. Place the blueberries, confectioners sugar, and lemon juice in a blender or food processor. Blend until fully combined. You can strain out the pieces of blueberry skin, but keeping them makes a very pretty glaze. If the glaze is not holding its shape, stir in a little more confectioners sugar to thicken it.