Preheat your oven to 400°F with a rack in the lower third.
Unroll the refrigerated pie crust and fit it into a 9-inch pie plate, letting the edges overhang slightly.
Fold the overhang under itself and crimp or press with a fork, then chill the crust for 20 minutes.
Prick the bottom and sides with a fork, line with parchment, then fill with pie weights or dried beans.
Bake the crust for 12 to 15 minutes, until it looks set and the edges are just starting to color.
While the crust bakes, separate the egg, putting the white in one small bowl and the yolk in another. Lightly beat the egg white with a fork and set it near the oven.
As soon as the crust comes out, remove the parchment and weights. Quickly brush the warm bottom with the beaten egg white to help seal and prevent a soggy crust.