Instructions

1. Melt 4 ounces chopped bittersweet chocolate in a microwave on medium power (about 45 to 90 seconds) or on the stovetop over medium-low heat. Whisk in 1/4 teaspoon espresso powder, if using, and set aside to cool to room temperature, about 20 minutes.
2. Whip 1 cup cold heavy cream in a medium bowl with an electric mixer on high speed until stiff peaks form, 2 to 3 minutes. Cover and refrigerate.
3. Place 1 1/2 sticks room temperature unsalted butter in the bowl of a stand mixer fitted with a paddle attachment. (Alternatively, use an electric hand mixer and large bowl.) Beat on medium speed for 1 minute. Add 1 cup granulated sugar and continue beating until light and fluffy, 3 to 5 minutes more. Add 1 teaspoon vanilla extract and cooled chocolate and beat until incorporated, about 1 minute. Add 2 of the eggs and beat on medium speed for 3 minutes. Add the remaining egg and beat until the mixture is silky and smooth, about 3 minutes more.
4. Add the whipped cream to the chocolate filling and fold with a rubber spatula by hand until no visible white streaks remain. Transfer the filling to the prepared pie crust and smooth into an even layer with an offset spatula. Refrigerate for a minimum of 2 hours, but preferably overnight. Decorate the pie with freshly whipped cream or dollop a spoonful onto each slice, and decorate with chocolate shavings if desired.