Add the flour, granulated sugar, baking powder, and salt to the bowl of a food processor and pulse three times to combine.
Add the very cold butter pieces and pulse at one-second intervals until the butter is mixed in.
Add the egg and pulse until the dough forms a ball on the blade of the processor
Turn the dough out of the food processor onto a floured surface, and carefully remove the blade.
Flatten the dough into a disc. Wrap it with plastic wrap and chill for 15-20 minutes.
Use a rolling pin to roll out pie dough into a circle that is 2 to 3 inches wider than the pie pan.
Carefully roll the dough onto the rolling pin and transfer it into your pie pan.
Refrigerate until needed.
Preheat oven to 375 degrees.
Separate one egg, placing the white and yolk into separate bowls.
Beat the egg white, then brush the crust with beaten egg white.
Place the pie crust on the center rack of a preheated oven and par-bake the crust for 7-8 minutes.
Remove the crust from the oven and place it on a wire rack to cool for 10 minutes.