In a mixing bowl, combine graham cracker crumbs, melted butter, sugar, and a pinch of salt until the mixture resembles wet sand. Press this mixture firmly into the bottom of 6-8 individual tart pans or ramekins, creating an even layer. Ensure the crust is compact, then refrigerate for at least 15 minutes to set.

In a saucepan, heat 1¾ cups of milk over medium heat until steaming, but not boiling. While the milk warms, whisk together sugar, cornstarch, and salt in a bowl. In a separate small bowl, whisk the egg yolks with a little remaining sugar, then gradually add cold milk to temper the yolks, mixing well before combining with the hot milk. Cook the mixture for 2-3 minutes, stirring frequently, until thickened, then remove from heat and stir in butter and vanilla.

Pour the banana custard into a clean bowl and cover it with plastic wrap, pressing it directly onto the surface to prevent a skin from forming. Allow the custard to cool at room temperature for about 10-15 minutes, then refrigerate for at least 30 minutes or until completely chilled and set.

Once the crusts are chilled and the custard has cooled, it's time to assemble. Slice ripe bananas just before use to prevent browning, and layer the banana slices evenly into the chilled crusts. Spoon the cooled banana custard over the bananas, ensuring it fills the crusts evenly. Smooth the tops with a spatula and return them to the refrigerator to chill for an additional 15-30 minutes.

In a mixing bowl, beat heavy cream with powdered sugar and vanilla extract on medium speed until soft peaks form. Be careful not to over-whip, as you want a silky, smooth texture for your topping.

Once the mini pies are set and chilled, carefully spoon a generous amount of whipped cream onto each pie. Garnish each pie with additional banana slices and perhaps a sprinkle of graham cracker crumbs. Serve these delightful treats chilled for the best flavor and texture!