Have ready a fully baked pie crust.
Beat sugar and butter for 10 to 15 minutes using the whisk attachment of a stand mixer. The goal is to make it less grainy. Even after 15 minutes, mine was still slightly grainy, but it smoothed out after adding the eggs.
Beat in the chocolate and vanilla, then add two of the eggs and beat for another 5 minutes. Add two more eggs and beat for 5 minutes. Pour into cooled pie crust. Chill 2 hours or until firm. Before serving, top with whipped cream and a little grated chocolate.