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. Use a thermometer to ensure temperature.
Remove from heat, then stir in the melted chocolate and vanilla until smooth.
Pour mixture into a medium bowl and let it cool to 75°F. Stir occasionally to help cool down.
Using a stand or an electric mixer, beat the butter until light and fluffy, about 2 to 3 minutes.
Gradually add in the cooled chocolate mixture then beat on high speed for 5 minutes, or until light and fluffy.
In a separate bowl, use a stand or an electric mixer to beat the cream, sugar and vanilla together until it begins to thicken and stiff peaks form.
Divide whipped cream in half and fold half into the chocolate mixture.
Save the other and chill in the refrigerator.
Pour the chocolate mixture into the crust, smoothing evenly. It will fill the entire dish.
Cover and chill for 4-6 hours until completely set. Pie can be made 24-48 hours ahead.
Top with remaining whipped cream and garnish with shaved chocolate.