Cut pie crust in half. Repackage and refrigerate 1 half for another use. On a lightly floured surface, roll out remaining half into an 8-in. circle. Transfer to a 7-in. pie plate; flute edge.
Line crust with a double thickness of heavy-duty foil. Bake at 450° for 4 minutes. Remove foil; bake until crust is golden brown, about 2 minutes longer. Cool on a wire rack.
Blend sugar and eggs in a small saucepan. Stir frequently over low heat until mixture reaches 160° and coats a metal spoon. Get off the heat. Smoothly mix chocolate and vanilla. Mix occasionally as it cools to 90°.
In a small bowl, cream butter until light and fluffy, 3-4 minutes. Add cooled chocolate mixture; beat on high speed until light and fluffy, about 5 minutes.
In another large bowl, beat cream until it begins to thicken. Add confectioners' sugar; beat until stiff peaks form. Fold into chocolate mixture.
Pour into crust. Chill for at least 6 hours before serving. Garnish with whipped cream and chocolate curls if desired. Refrigerate leftovers.