In a small saucepan, whisk together the granulated sugar and eggs.
Set over medium-low heat and cook, whisking constantly, until the mixture reaches 160°F and coats the back of a metal spoon.
Remove from heat and stir in the melted chocolate and vanilla until smooth.
Set aside to cool to room temperature; stirring occasionally.
In a large bowl, using an electric mixer, on high speed, beat the butter until light and fluffy; about 2 to 3 minutes.
Gradually add in the cooled chocolate mixture and beat, on high speed,for 5 minutes, or until light and fluffy; set aside.
In a separate large bowl, use an electric mixer, on high speed, to beat the cream until it begins to thicken.
Add the confectioners' sugar and beat until stiff peaks form; fold into the chocolate mixture.
Pour the mixture into the prepared crust, smoothing evenly.
The pie will be tall with filling.
Chill for 6 hours.
At this point, the pie can be stored for up to 2 days ahead of time.