Whisk together the egg yolks in a small bowl. Set aside. In a medium-sized saucepan, whisk together the sugar, cornstarch, and salt. Add the milk and whisk until fully incorporated. Place on the stove over medium heat and cook, whisking constantly until the mixture begins to thicken and just starts to boil. Remove from the heat.
Temper the egg yolks by slowly adding about 1 cup of the hot thickened milk/cornstarch mixture to the bowl while whisking briskly. Add the tempered egg mixture back into the pot and turn the heat on to medium again and whisk constantly until the mixture begins to boil and registers at least 165℉(74℃) on a candy or meat thermometer(to ensure the egg yolk is fully cooked).
Pour the custard immediately into a heat-safe mixing bowl and add the vanilla and banana extracts. Whisk until combined. Place a piece of plastic wrap over the top of the custard, pressing the wrap right against the custard to prevent a skin from forming. Let cool at room temperature until just barely warm. Don't leave out for over 2 hours, place in the fridge (on a hot mat) after about ½ hour at room temp if you want to speed it up. While the custard is cooling, make the crust for the pie.
To make the Crust:
Preheat the oven to 350℉. Stir together the graham crumbs, sugar, and cinnamon in a mixing bowl. Stir in the melted butter to combine. Pour the crust mixture into a 9-inch pie pan and press firmly onto the bottom and sides of the pan to form a crust. Bake in the preheated oven for 10-12 minutes. Let cool completely on a wire rack until ready to assemble the pie.
To assemble the Pie:
Once both the custard filling and pie crust are cooled to room temperature it is time to assemble the pie. Slice 2 (or 3 small) bananas into ¼-inch slices and arrange in one layer on top of the crust. Cover the banana slices with the custard, smoothing the top with a spatula. Cover the pie, placing the plastic wrap directly against the top of the custard to prevent a skin from forming. Refrigerator for at least 6 hours or overnight is best.
To make the Whipped Cream:
Mix together the whipping cream and powdered sugar in a large mixing bowl, then whip using a handheld electric mixer on high speed until stiff peaks form. Top the finished, chilled pie with the whipped cream just before serving. Enjoy!
Notes
The finished pie will stay fresh if stored covered in the refrigerator for up to 2 days.