Cut the butter into ½-inch chunks and let chill in the freezer for 10 minutes to get extra cold.
Pour the water into a cup and fill it with ice cubes. Set aside.
Add the flour, sugar, and salt in the bowl of an electric stand mixer fitted with the paddle attachment and mix on low speed to combine.
Turn off the mixer and add the chilled butter to the flour mixture. Mix on low speed for 30 seconds - 1 minute until the butter resembles the size of walnut halves.
Gradually pour in ¼ cup of the ice cold water (without the ice cubes). Mix for another 30 seconds - 1 minute just until the dough starts to barely come together (you don’t want to overmix it into a ball like cookie dough). The dough should be very shaggy and you should still be able to see big chunks of butter. If you need more water, then add one tablespoon at a time.
Transfer the dough to a lightly floured surface and shape into a disc. Wrap in plastic wrap and refrigerate for at least 1 hour or overnight. To make ahead, wrap the dough in extra plastic wrap and freeze it. Then defrost in the fridge overnight one day before you are ready to use it.
Blind bake the pie dough
Roll out the dough into an 11-inch circle on a lightly floured work surface. Transfer it to a 9” pie dish. Trim the edges with kitchen scissors, leaving a ½ inch overhang around the edges. Tuck the overhang under the edge and crimp.
Dock the bottom and sides of the pie shell with a fork to prevent the dough from puffing up with steam while it bakes. Let chill for 30 minutes in the refrigerator or freezer if you are using a metal pie plate (Note: Do NOT freeze if using a glass pie dish to ensure the change in temperature from the freezer to oven does not crack it).
While the dough chills, preheat the oven to 425°F.
Crumple up a piece of parchment paper that is big enough to line the entire pie shell. Place it in the pie shell and fill the pie shell with dried rice or beans. This will act as pie weights.
Bake for 15-20 minutes until golden brown. Carefully remove parchment paper along with the rice or beans. Beat the egg and 1 tablespoon of water together to make an egg wash. Brush the entire pie shell with egg wash. Bake for another 5-10 minutes until golden brown and completely cooked. Let cool on a wire rack.
For the chocolate pudding
Transfer the chopped chocolate or chocolate chips to a heat-safe bowl. Set aside.
Fill a saucepan with about 2 inches of water and heat on medium-low until it just begins to simmer. Place the bowl of chopped chocolate over the hot pot of water (you do not want the bottom of the bowl to be touching the water) and then turn off the heat to gently heat it. Stir until melted and set aside.
In a small bowl, whisk together sugar, cornstarch, and cocoa powder until combined. Set aside.
In a saucepan, add the heavy cream, milk, and salt and place on medium heat. Once the milk just barely starts to bubble and simmer, remove from heat. Whisk in the sugar, cornstarch, and cocoa powder mixture. Return to heat and bring to a boil over medium heat, whisking constantly. Once boiling, cook for 2-3 minutes until thickened and the cornstarch has cooked.
Remove from heat and whisk in the melted chocolate and vanilla extract and whisk until smooth.
Pour the chocolate pudding into the cooled and baked pie shell and spread and smooth it out with an offset spatula. Cover with wax paper or plastic wrap to prevent a skin from forming, ensuring the wax paper or plastic wrap is completely smooth because it will show any creases once cooled and congealed. Refrigerate for 3-4 hours until cold and set.
For the whipped cream topping
Right before serving, whisk the heavy whipping cream using a hand mixer or an electric stand mixer with the whisk attachment (you’re welcome to use a whisk if you’re looking for a workout!). Whisk on medium-high speed just until it holds soft peaks or until its reached your desired consistency, about 3-4 minutes.
Spoon the whipped cream on top of the chilled pie and sprinkle with chocolate shavings (I use a vegetable peeler to make my chocolate shavings). Serve immediately. Enjoy!
Notes
Whipped cream is best served immediately as it is not very stable. If you do make it ahead, whip the heavy cream just until it has reached soft peaks. Cover it tightly and store it in the refrigerator to keep it cold. Then, right before serving, re-whip it for a few seconds to revive it a bit.