In a microwave-safe bowl, microwave ½ cup butter until melted. Set aside.
In a medium bowl, stir together graham cracker crumbs, ½ cup sugar, and melted butter until combined. Using the bottom of a measuring cup, press mixture into bottom and up sides of a 9-inch pie plate. Refrigerate 15 minutes.
In a medium bowl, place chopped chocolate. In a small saucepan, bring cream and remaining 2 tablespoons butter to a boil over medium- high heat. Pour over chopped chocolate, whisking until smooth. Pour into prepared crust; refrigerate 30 minutes.
Arrange banana slices over chocolate layer. In a medium saucepan, cook half-and-half and vanilla over medium heat, stirring frequently, until mixture begins to simmer, 3 to 5 minutes. 5. In a medium bowl, whisk together remaining ½ cup sugar and cornstarch. Add eggs and egg yolk, whisking until smooth. Gradually add hot half-and-half mixture to egg mixture, whisking well after each addition. Transfer mixture to saucepan; cook over medium heat, stirring constantly, until mixture comes to a boil and thickens, approximately 6 minutes. Strain through a fine-mesh sieve into a medium bowl. Refrigerate 20 minutes.
Spread cooled custard over banana layer; refrigerate 2 to 4 hours, or up to 3 days. Top with whipped topping just before serving.
Recipe by Taste of the South at https://tasteofthesouthmagazine.com/black-bottom-banana-cream-pie/