For the crust: Line a 9-inch pie plate with the All-Butter Easy Pie Dough. Dock the bottom and refrigerate for 30 minutes.
Preheat the oven to 350 degrees F.
Line the crust with parchment, fill it with pie weights or dried beans and bake it for 15 minutes. Remove the pie weights and parchment and bake the crust for 10 minutes more, or until the bottom begins to turn golden brown and is cooked through. Set aside to cool completely.
For the ganache: In a heavy saucepan over low heat, combine the cream, butter and vanilla and cook, stirring, until the butter has completely melted. Increase the heat to medium high and bring the mixture to a simmer. Remove the pan from the heat and pour in the chopped chocolate. Leave the pan undisturbed for a few minutes to allow the chocolate to melt. Whisk until the ganache has emulsified and is shiny.
For the pastry cream filling: Whisk together the milk, cream, granulated sugar, cornstarch, vanilla, salt and egg yolks in a heavy saucepan over medium heat until thickened and just starting to bubble. Transfer to a large bowl and stir in half the chocolate ganache until well combined. Place a piece of plastic wrap on the surface and let cool in the refrigerator at least 1 hour
For the assembly: Pour the remaining ganache into the crust and, using the back of the spoon or an offset spatula, spread it along the bottom and up the sides until the inside of the crust is completely coated; let it set up in the refrigerator, at least 15 minutes. Once the ganache has set, spread the pastry cream filling into the crust and refrigerate while you make the whipped cream.
Whip the cream in a medium bowl with an electric mixer fitted with the whisk attachment until it begins to thicken. Add the confectioners' sugar and cocoa powder and continue to beat until it holds stiff peaks.
Gently spoon the whipped cream on top of the pastry cream and spread it carefully and evenly until it just touches the edges of the dough. Chill the pie in the refrigerator for a few hours to set.
Before serving, melt the chocolate pieces and drizzle chocolate over the pie.
All-Butter Easy Pie Dough:
In the bowl of a food processor fitted with the blade attachment, pulse together the flour, salt, sugar and butter until the mixture resembles cornmeal with some pea-size pieces of butter remaining.
In a small bowl, stir together the ice water and the lemon juice. Slowly add the liquid to the flour mixture, pulsing, until the dough just comes together. Squeeze a small piece of dough between your thumb and index finger to make sure it holds its shape.
Turn the dough out onto a lightly floured surface and divide it in half. Gently turn over each piece of dough a few times so that any dry bits are incorporated. Form each piece into a loose disk, wrap in plastic and refrigerate for at least 20 minutes.