Combine the milk and vanilla bean in a heavy saucepan and bring just to a simmer. Remove from the heat and allow to sit for at least 15 minutes. Return just to a simmer and in a large bowl combine the sugar, egg, egg yolks and cornstarch and whisk until pale yellow and sugar and cornstarch are thoroughly incorporated. Add 1 cup of the hot milk mixture to the egg mixture and whisk to combine. Pour the egg mixture into the hot milk and whisk to combine. Return to the heat and cook over medium heat, stirring constantly, until thick and smooth, about 5 minutes. Remove from the heat and strain custard through a fine mesh sieve into a clean bowl. Whisk in the butter, place a piece of plastic wrap directly on the surface of the custard to prevent a skin from forming, and set aside to cool completely.
While the custard is cooling, prepare the pie crust dough according to recipe directions and allow to rest, refrigerated, for at least 1 hour before rolling out the dough. On a lightly floured surface with a lightly floured rolling pin, roll the dough out to a thickness of 1/8-inch and fit into a deep dish pie pan. Trim the edges and crimp decoratively if desired. Refrigerate for at least 20 minutes.
Preheat the oven to 400 degrees F.
Line the pastry with a piece of parchment paper and fill with pie weights. Bake for 16 to 18 minutes, or until the pie crust is light golden around the edges. Remove the parchment and continue to cook until the pie crust is golden brown around the edges and lightly golden on the bottom and sides, about 3 minutes longer. Reduce the oven temperature to 350 degrees F. and remove the pie crust from the oven. Using a pastry brush, lightly brush the inside bottom and sides with some of the egg white. Allow to cool slightly then transfer the cooled custard to the pie pan and place the filled pie crust in the oven. Bake the pie until the crust is golden brown and the custard is set, about 20 minutes longer. Remove from the oven and allow to cool on a wire rack. Chill thoroughly before serving.
Basic Sweet Crust:
Sift the flour, sugar, and salt into a large bowl. Using your fingers, work in the butter and shortening until the mixture resembles coarse crumbs. Add 2 tablespoons of ice water and work with your fingers until the water is incorporated and the dough comes together. Add more water as needed to make a smooth dough, being careful not to over-mix. Form the dough into a disk, wrap tightly in plastic wrap, and let rest in the refrigerator for at least 30 minutes.
Yield: 1 single pie crust