Preheat the oven to 375°F. Fit the crust into a 9-inch pie plate, crimp the edges, and chill the crust for 10 to 15 minutes.
Line the crust with parchment or foil and fill with pie weights or dry beans. Bake 12 to 14 minutes. Remove weights and parchment, then bake 5 to 7 minutes more, just until the bottom looks set.
(Optional) Brush the warm crust lightly with egg white. Reduce oven temperature to 325°F.
In a large bowl, whisk the eggs, sugar, flour (or cornstarch), and salt until smooth.
Warm the milk and cream in a saucepan over medium heat until hot and steamy (do not boil).
Temper the eggs by slowly whisking about ½ cup of warm milk into the egg mixture. Then slowly whisk in the remaining milk mixture. Stir in the vanilla.
Strain the custard through a fine-mesh strainer, then pour into the warm crust. Sprinkle nutmeg on top.
Bake 35 to 45 minutes, until the edges are set and the center still jiggles gently. Cool on a rack for 1 hour, then refrigerate at least 4 hours before slicing.