For the Pie Dough:

1. Place 3 cups Cup4Cup flour, sugar and salt in a food processor and pulse to evenly distribute.
2. Add in 1 cup cold, cubed butter, pulsing until the mixture resembles coarse meal.
3. Transfer mixture into a large bowl and set aside.
4. Combine the egg and the buttermilk together in a small bowl. Create a well in the flour mixture, gradually whisk in the egg mixture with a fork until it forms a ball.
5. Wrap the dough in plastic wrap and rest in refrigerator for 30 minutes.
6. Cut the dough in half. Using extra Cup4Cup flour to prevent sticking, roll out one portion and drape to into a 9-inch pie dish, about 1/8-inch thick.
7. Refrigerate the other half until ready to use.

For the Filling:

1. Preheat oven to 350°F.
2. In a large bowl, mix together blueberries with the lemon zest and juice, ginger, flour, sugar, and salt. Place the fruit mixture in a pie dish lined with half of the rolled out pie dough.
3. Dot the top of the filling with the 2 tablespoons butter evenly.
4. Taking the other half of the pie dough cover the pie crust. Use a full crust, or cut into strips and make a lattice top. Crimp the edges together. If using a full crust, cut a slit in the top to allow steam to escape.
5. Egg-wash the top and lightly sprinkle the coarse sugar evenly on top, if desired.
6. Bake for 45 minutes to 1 hour or until golden brown and the filling is bubbling.
7. Cool for at least 1-2 hours to allow the filling to set before slicing.