How to Make It
Preheat the oven to 350°. In a food processor, combine the graham cracker crumbs with the sugar, cinnamon, salt and melted butter and pulse until the crumbs are moistened. Press the crumbs evenly into a 9- to 10-inch, deep-dish glass or ceramic pie plate. Bake for about 8 minutes, until the crust is lightly browned and set. Let cool completely.
In a large saucepan (preferably with a rounded bottom), combine the granulated sugar with the cornstarch, egg yolks and 1/2 cup of the milk and whisk until smooth. Whisk in the remaining 2 cups of milk and cook over moderate heat, whisking constantly, until the custard is very thick, about 5 minutes. Remove from the heat and whisk in the butter and vanilla extract until the butter is melted. Pour half of the vanilla custard into a medium bowl.
Whisk the chopped chocolate into the custard in the saucepan until it is melted. Spread the chocolate custard evenly in the pie crust and top with the sliced bananas. Carefully spread the vanilla custard over the bananas. Refrigerate the banana cream pie until it is well chilled, at least 6 hours and preferably overnight.
In a medium bowl, using an electric mixer, beat the heavy cream with the confectioners' sugar until it is softly whipped. Mound the whipped cream on top of the pie. Garnish the banana cream pie with chocolate shavings and serve.