Filling:
1. Whisk sugar, cocoa, and cornstarch in heavy medium saucepan. Gradually whisk in half and half and then the egg yolks. Continue to whisk over medium-high heat until mixture thickens and boils, about 12 - 15 minutes.
2. Remove from heat and add both chocolates and butter, whisking until melted and smooth. Mix in coffee liqueur and vanilla. Transfer filling to crust. Press plastic wrap directly onto surface of filling and chill until filling sets, at least 6 hours. (Can be made 2 days ahead. Keep chilled and covered.)
Topping:
1. Beat all ingredients in large bowl until peaks form. (Can be made 1 day ahead. Cover and refrigerate. Rewhisk to thicken and smooth before serving, if necessary.)
2. Peel plastic off of pie. Cut pie into fairly small wedges (it is quite rich). Spoon a good-sized dollop of coffee whipped cream on top of each slice. Garnish with chocolate-covered espresso beans and serve.after-thoughts:This pie would also be delicious