Preheat oven to 350 degrees. Spray a 9-inch pie plate with nonstick cooking spray.
In a medium bowl, thoroughly mix chocolate wafer crumbs, sugar, and melted butter. Evenly press crumb mixture into prepared pie plate. Bake crust for 8 minutes. Cool on a wire rack. Set aside.
Meanwhile, whisk together cornstarch, cocoa powder, and salt in a medium bowl. Add 2 tablespoons of the half and half and mix to a smooth paste consistency. Whisk in remaining half and half and set aside.
Mix milk, sugar, and chocolate in a heavy bottom, medium saucepan. Over medium heat, stirring constantly, melt the chocolate completely. Remove pan from heat and mix about 1/2 cup of the melted chocolate mixture into the half and half mixture. Add this mixture to the remaining chocolate mixture in the saucepan. Return the saucepan to the cooktop and, over medium heat, cook mixture stirring constantly. Bring to a boil. Continue to cook, stirring constantly, for 1 minute. Take the pan off the cooktop and add butter and vanilla and stir until smooth. Pour into cooled pie crust. Cover and refrigerate until completely chilled; about 6 hours.
When the pie is completely chilled make whipped cream; in a medium bowl, using an electric mixer beat cream, sugar, and vanilla until soft peaks form. Spread whipped cream decoratively over pie. Top with chocolate curls or shavings. Serve immediately.