For the filling:
1 cup heavy cream, chilled
3 large eggs
¾ cup sugar
2 tbsp. water
8 oz. bittersweet chocolate, melted and cooled
1 tbsp. vanilla extract
8 tbsp. unsalted butter, softened and cut into 8 pieces
Freshly whipped cream, for serving
Roll the chilled pie dough into a 12-inch circle. Line a 9-inch pie plate with the dough. Trim, fold and crimp the edges. Cover with plastic wrap and freeze for 30 minutes.
Preheat the oven to 375˚ F and adjust an oven rack to low-middle position. Line the chilled pie shell with parchment paper so that it lays over the edges of the dough. Fill with pie weights and bake until the surface of the dough no longer looks wet, 20-25 minutes. Remove the pie weights and parchment paper and return the pie crust to the oven. Bake until the crust is golden brown, 10-12 minutes more. Transfer to a wire rack and let cool.
To make the filling, add the cream to the bowl of an electric mixer. Whip on medium-high speed until stiff peaks form. Transfer to a small bowl and refrigerate.
Combine the eggs, sugar and water in a heatproof bowl set over a saucepan of simmering water (the water should not touch the bowl). With a hand mixer on medium speed, beat until the egg mixture is thickened and reads 160˚ F on an instant read thermometer, about 7-10 minutes. Remove the bowl from the heat and continue to beat until the egg mixture is fluffy and cooled to room temperature, about 6-8 minutes.
Add the melted chocolate and the vanilla to the cooled egg mixture and beat until well blended. Beat in the butter 1 tablespoon at a time until well combined. Using a spatula, gently fold in the chilled whipped cream until no streaks remain. Transfer the filling to the baked pie shell. Refrigerate until set, at least 3 hours. Slice and serve with freshly whipped cream as desired.