- For the crust, preheat the oven to 350ºF. Stir the graham crumbs, sugar and melted butter together until evenly combined and press this into a lightly greased 9-inch pie plate. Bake the crust for 10 minutes, then cool while preparing the filling.
- For the filling, whisk the sugar, cornstarch and salt in a medium saucepot. Whisk in the milk and place this over medium heat, whisking until it reaches a full simmer and becomes thick and glossy. Remove the pot from the heat and pour this over the chopped chocolate, stirring until smooth. Have the egg yolks in a separate, smaller bowl, and whisk about a cup of the chocolate cream into the yolks, then add this and the chocolate mixture back to the pot, whisking over low heat for one minute and stir in the vanilla. Pour this into the cooled pie crust and immediately cover the filling with plastic wrap directly on the surface. Cool for 15 minutes, then chill for at least 4 hours to set.
- For the topping, whip the cream to a soft peak and whip in the icing sugar and vanilla. Spread this over the chocolate cream and serve.
- The crust and chocolate cream can be prepared a full day in advance, but the topping should be made within four hours of serving.