Adjust an oven rack to the lower middle position and heat the oven to 375°. Remove the prepared pie shell from the freezer. Line the chilled pie crust with a double layer of foil, covering the edges to prevent burning, and fill with pie weights or pennies. Bake until the dough looks dry and is light in color, 20 to 25 minutes. Remove the weights and foil and continue to bake until the crust is deep golden brown, 10 to 15 minutes. Set aside to cool to room temperature.
In medium bowl, whip cream with vanilla with mixer on medium low speed until frothy, about one minute. Increase the speed to high and continue to whip until the cream forms stiff peaks, 1 to 3 minutes. Cover and refrigerate until needed.
Combine the eggs, sugar, and water in a large heatproof bowl set over a medium pan filled with 1/2 inch barely simmering water. Don't let the bowl touch the water. Beat with electric mixer on medium speed until the egg mixture is thickened and registers 160°, 7 to 10 minutes. Off the heat, continue to beat the egg mixture until fluffy and cooled to room temperature, about eight minutes longer.
Add the cooled chocolate and vanilla to the egg mixture and beat until incorporated. Beat in the butter, a few pieces at a time, until well mixed. Using a spatula fold in the whipped cream until no streaks of white remain. Scrape the filling into the cooled pie shell and refrigerate until set, at least three hours, and up to 24 hours.. Serves eight