Crust: Make the flaky pie crust and chill per the recipe. Roll the crust and press it into a greased 9-inch deep dish pie pan. Cut any excess dough, leaving a 1/2-1 inch overhang. Fold overhang under itself, creating a thicker ring of crust around the edge. Use the finger pinch method to crimp the edge. Dock the bottom with the tines of a fork. Brush a sheet of aluminum foil liberally with butter or spray with cooking spray. Place the buttered surface inside the pie shell, pressing onto the crust. Freeze for 1 hour or overnight.
Blind Bake Crust: Preheat oven to 350°F. Fill the crust with beans or pie weights. Bake the crust with foil for 20 minutes. Remove the foil and weights. Continue to bake another 10-15 minutes, baking until the crust is golden brown. Set aside to cool.
Make Chocolate Filling: Bring 2-inches of water to boil in the bottom of a double boiler. In a heat proof bowl, whisk together eggs and sugar. Place the bowl over the simmering water. Whisk regularly until the mixture reaches 165°F with an instant read thermometer. Remove from heat and allow to cool until just warm.
Melt Chocolate: While egg mixture is cooling, chop the bittersweet chocolate and place in a microwave safe bowl. Microwave in 30 second intervals at 50% power, stopping to stir between each interval. Repeat the process until mixture is completely melted.
Add the espresso powder to the melted chocolate stirring to fully combine. Pour the egg mixture over the melted chocolate and whisk until fully incorporated. Allow to cool to room temperature.
Make the Filling: In a large bowl use an electric mixer to cream the butter beating until fluffy. Add 1 tsp vanilla extract mixing on low speed just until combined.
With the mixer on low speed gradually add chocolate mixture stopping to scrape down sides of the bowl periodically. Increase the speed to medium-high, beating until the mixture increases in volume and lightens in color, about 5 minutes.
Whipped Cream: In a clean large bowl of a stand mixer fitted with the whisk attachment (or using a hand mixer) beat together heavy cream, 1 tsp vanilla extract and powdered sugar to stiff peaks.
Gently fold 1/2 of the whipped cream into the chocolate mixture. Next, add the remaining whipped cream, gently folding until no white streaks of cream remain.
Pour the chocolate filling into the crust. Level the surface with an offset icing spatula.
Refrigerate for at least 8 hours or overnight. Garnish with additional whipped cream and shaved chocolate, if desired.
Cook's Note: To make extra whipped cream for the topping you'll need an additional 1 cup of heavy cream and 1/4 cup of powdered sugar. Use 2/3 of the whipped cream for the filling and decorate the top with the remaining whipped cream. You can also use Cool Whip for the topping.