Making the Pastry:

1. In a bowl, whisk together the flour, baking powder, sugar, salt and lemon zest.   
2. Add the butter in chunks, then using a pastry cutter (or your hands) cut the butter into the dry ingredients to form small, pea-sized clumps.
3. Then add the sour cream and bring the mixture together by hand, to form a ball of dough.
4. Place the dough onto a floured surface, then roll it out into a rectangular shape.
5. Fold the dough over onto itself in thirds, rotate by 90 degrees and roll out into a rectangular shape again.
6. Repeat these steps two additional times.
7. Cover the dough with plastic wrap and refrigerate for at least one hour.

Making the Blueberry Pie Filling:

1. Place the blueberries into a saucepan over low-medium heat and simmer until the berries release their juices.  Simmer for about 10 minutes, stirring often. 
2. In a separate small bowl whisk together the sugar and cornstarch, until it is thoroughly combined. Mixing these 2 ingredients well will ensure that the cornstarch does not clump.
3. Stir the sugar/cornstarch mix into the blueberries while you continuously stir.  Simmer the mixture until the filling has thickened. This won’t take very long at all…about 5-10 minutes. 
4. Stir in the lemon juice and vanilla.  Mix well.
5. Remove the filling from the heat and let cool. 

The Egg Wash:

1. In a small bowl whisk together the egg and milk. Set aside.

Putting the Pies Together:

1. Preheat your oven to 425 degrees.
2. Assembling the hand pies: On a floured surface, roll the chilled dough into a rectangular shape, to about 1/8-inch thickness.
3. Using a 2- or 3-inch cookie cutter, cut uniform circular shapes into the pie dough. 
4. Place 6 – 8 circle cut outs onto a parchment paper lined cookie sheet.
5. Gather the remaining dough, roll it out and repeat until it has all been used. (you need a total of either 12 or 16 circles)
6. Now add a dollop of filling (about 1 to 2 tablespoons depending on the size of the circle) onto the centre of each circle (see the picture above).
7. Brush the edge of the dough with the egg wash, then place a second circle of dough on top, pressing the edges firmly together.
8. Crimp the edge using a fork.  (see the pictures above for reference)
9. Repeat process until all of the hand pies have been filled. 
10. Cut small slits for vents into the top of each pie using a sharp knife. (refer the image above to see how I cut 4 small slits into the tops)
11. Brush the top and edges of the pies with the egg wash.
12. Sprinkle with sugar.
13. Bake the pies for 18 minutes or until tops are golden brown.
14. Cool for about 5 minutes before serving.