Ashley | Baker By Nature

To make the crust:

In a large bowl whisk together the flour, salt, baking powder, and sugar.
Add the butter, working it in with your hands or a pastry cutter, until it's a coarse meal. The butter should still be in large, pea-sized pieces.
Using a rubber spatula, stir in the sour cream. The dough will be very shaggy at this point. Turn it out onto a well floured work surface, and bring it together with a few quick kneads.
Pat the dough into a 10 inch log, then roll it out into a 10" x 12" rectangle. Dust both sides of the dough lightly with flour, and starting with the shorter end, fold it in three - like a letter. Flip the dough over, and roll it again into a 10" x 12" rectangle. Fold it in three again. Wrap the dough in saran wrap, and chill for 1 hour.

To make the blueberry filling:

Combine all of the ingredients in a saucepan; bring to a simmer over medium-heat. Cook until the mixture starts to thicken, about 6 minutes. Transfer the blueberry filling to a bowl and let cool to room temperature.
Assembly and cooking:
Preheat the oven to 425°(F). place a rack on the middle shelf. Line a large baking sheet with parchment paper.
Roll the dough into a large square, about 16" x 16". For square pies, use a pastry wheel or pizza cutter to cut out sixteen even squares. For round pies, use a 4" biscuit cutter (or something round like the top of a martini or wine glass) to cut out 16 circles.

Divide the cooled filling among eight of the squares (or circles), using about two tablespoons for each. Brush a little bit of the beaten egg wash along the edges of each filled square (or circle).
Using a small knife, cut a vent into each of the remaining eight squares (or circles).
Top each filled square (or circle) with a vented square (or circle), and press along the edges with the fork or a pie crust crimper. Make sure the edges are sealed well!
Brush the top of each pie with the remaining beaten egg, and sprinkle with sugar, if using.
Transfer the pies to prepared baking sheet.
Bake the pies for 20 minutes. Remove them from the oven, and let cool for 20 minutes before serving.