Cut butter into 1/4" cubes and toss in the freezer while you prep your ingredients.
Place all dry ingredients in a food processor, and process a few times to combine.
Add butter (7 1/2 Tablespoons),whisked egg (1), and egg white (1). Pulse only until the dough becomes crumbly (about 8-10 pulses using 1-second intervals).
Form the dough into a ball and flatten it into a disc.
Wrap the dough in cling wrap and place in the fridge for at least 1 hour, or up to 3 days.
Meanwhile, butter a 9" pie pan.
Using a rolling pin, roll dough between two sheets of parchment until it forms a 13" circle.
Remove the top layer of parchment, and lay the dough over the pie pan. Then carefully peel back the bottom piece of parchment.
Fold the edges over and decorate as desired.
Place the pie pan in the freezer for 30 minutes.
Preheat oven to 425.
Optional Egg Wash: whisk the remaining egg, and use a small brush to put a thin layer of the egg on the edges of the crust.
To prebake crust, bake for 12-14 minutes, or until the edges are a nice golden brown.