Remove from heat and stir in the melted chocolate and vanilla extract until smooth. Let cool until warm, stirring occasionally.
While chocolate cools, add butter to a mixing bowl and beat until light and fluffy, 2-3 minutes. Gradually pour in the chocolate mixture, then beat on high until light and fluffy, about 5 minutes. Set aside.
In a separate bowl, beat the heavy cream with an electric mixer until it starts to thicken. Add powdered sugar and continue beating until stiff peaks form.
Fold 1 1/2 cups of the whipped cream into the chocolate mixture and reserve the rest for topping.
Spread chocolate mixture into cooled pie crust and chill until set, 1-2 hours. Top with remaining whipped cream and garnish with chocolate shavings, if desired, before serving.
Enjoy!