How to Make It
Make Crust: Roll pie dough to a 1/8-inch thick circle and place inside a greased 9-inch metal pie pan. Cut excess dough, leaving a 1/2-inch overhang. Fold overhang under itself, creating a thicker ring of crust around the edge. Crimp edge. Grease a sheet of aluminum foil liberally with butter. Place the buttered surface inside the pie shell, allowing the crust to come in direct contact with the foil. Freeze for 1 hour or overnight. Preheat oven to 350°F. Bake crust with foil for 20 minutes. Remove foil and use a spoon to press down any areas that have puffed up. Return to oven for an additional 13-15 minutes, until the crust is golden brown all over. Set aside to cool.
Make Filling: Bring 2 inches of water to boil in the bottom of a double boiler. Whisk together eggs and sugar and place over double boiler, whisking regularly until the mixture reaches 165°F. Remove from heat and allow to cool until just warm.
While egg mixture is cooling, chop the chocolate and place in a microwave safe bowl. Microwave for 20 second intervals at 30% power, stirring in between each interval, until mixture is completely melted. Pour egg mixture over melted chocolate and whisk until fully incorporated. Whisk in espresso powder. Allow to cool completely to room temperature.
In the bowl of a stand mixer fitted with the paddle attachment, beat butter until fluffy. With the mixer on low, slowly pour in chocolate mixture. Scrape down sides of the bowl with a spatula, and increase the speed to medium-high, beating until the mixture increases in volume and lightens in color, 5 minutes.
In a clean bowl, beat together cream and powdered sugar to stiff peaks. Gently fold half of the whipped cream into the chocolate mixture. Add remaining whipped cream and gently fold until no streaks of cream remain. Pour filling into crust, leveling the surface with a spatula. Refrigerate for 8 hours or overnight. Garnish with whipped cream and cocoa powder or shaved chocolate, if desired.