Preheat oven to 375°F.
Combine the ingredients for the crust in a bowl. Evenly distribute the mixture into portion cups. Press the mixture into the bottom so it is flat and compact.
In a medium saucepan, add half-and-half, banana, sugar, cornstarch and egg yolk; whisk until well combined. Place over medium heat and bring to a boil, stirring often. Boil for 1 minute, whisking constantly (it will become thick).
Remove from heat and add butter and vanilla extract; stir until well combined and butter has completely melted.
Cover with plastic wrap, pressing the plastic wrap directly onto the filling so its touching (this will prevent a skin from forming on the custard). Let sit at room temperature for 30 minutes.
Spoon the mixture over the graham cracker crust. Cover and refrigerate for about 1 hour.
Using an electric mixer or by hand with a whisk, whip the heavy cream until stiff peaks form.
Top the pies with whipped cream before serving.