Normally pastry dough is made with butter, but the vinegar and shortening in this recipe yield a very flaky, tender crust. Seek out a solid vegetable shortening that doesn't contain unhealthy hydrogenated oil (such as Spectrum).
This is a good recipe for beginning pie makers: the dough is easier to work with and more forgiving than an all-butter crust.
Place the flour and salt in a large bowl and whisk to combine. Add the chilled shortening. Using the back of a fork or a pastry blender, cut the cubes into the flour until the mixture resembles coarse meal.
In a small bowl whisk together the ice water, 2 tablespoons of the beaten egg, and the vinegar. Add this mixture to the flour, and toss with a fork or your fingers until the dough is moist and begins to clump together.
Gather the dough into a ball and cut it in half. Flatten each ball into a disk and wrap them separately in plastic. Refrigerate the dough at least 2 hours (or up to 2 days) before rolling out. The dough disks may also be frozen, if you wrap them tightly in plastic and then place them in airtight bags. Defrost overnight in the refrigerator before using.