Add the flour, baking powder, and salt to the bowl of the food processor. Pulse a couple of times to combine. Evenly distribute butter cubes in the flour mixture. Pulse until the butter pieces are pea-sized. Then spoon in the sour cream. Pulse until the dough looks wet and crumbly. It will NOT come together in the bowl, and you don't want to mix it to the point where it does. Turn it out onto a floured surface and give it a few kneads to get it to come together.

Roll into an 8x10 inch rectangle. Fold the dough in thirds (like a business letter). Flip dough over, and rotate it 90º. Roll into another 8x10 inch rectangle and fold in thirds. Wrap in plastic wrap and pop it in the fridge to chill for at least 30 minutes. 

When the dough has almost been in the fridge for 30 minutes, combine filling ingredients in a separate bowl and prepare egg wash in another. Preheat oven to 425º. Have a rolling pin, pastry frame (or floured surface), pizza or pastry cutter, pastry brush and two baking sheets lined with parchment paper. As soon as you get the dough out of the fridge, you'll want to work fast! Roll dough into a 14x14 inch square. Cut squares that are 3 1/2 inches tall and wide. At the end, you'll have 16 squares. 

Place the filling on half of the squares, making sure it's evenly distributed (about 1-2 tablespoons of filling-you may have some leftover and that's okay). Brush the edges of the filled squares with the egg wash and top with the rest of the squares. Seal the edges with a fork and cut some slits on the top. Brush the remaining egg wash on top of each pie. Pop them in the oven to bake for 15-20 min or until they are puffy and golden brown.

Let cool a few minutes and place them on a cookie rack over a baking sheet. Allow to cool almost completely. While they are cooling, whip up the glaze. Lightly drizzle the glaze over each pie. Enjoy!