⅔ cup granulated sugar 2 large eggs 2 ounces unsweetened chocolate, chopped 1 teaspoon pure vanilla extract ⅓ cup (⅔ stick) unsalted butter, at room temperature ⅔ cup heavy cream ¼ cup powdered sugar 1 prebaked 9-inch pie crust or tart shell (as shown) or Chocolate Cookie Crust (see below) Whipped cream and shaved dark chocolate (optional), for garnish