Move the oven rack to the middle position and preheat the oven to 350F.
MAKE GRAHAM CRACKER CRUST:
Crush graham crackers in a food processor or crush them in a plastic zip-top bag with a rolling pin.
In a large mixing bowl, combine the graham crackers, cooled melted butter, and sugar until well combined.
Spread and press down the crust mixture into a 9-inch pie dish with your hands.
Bake the pie crust in your preheated oven for 10 minutes.
Remove the crust from the oven and allow it to cool completely.
Then place the crust into the refrigerator to chill until ready for use.
MAKE THE CUSTARD:
Mix the granulated sugar, cornstarch, and salt in a medium-sized saucepan until combined. Pour in the milk slowly, constantly whisking until the milk mixture thickens, keeping just under a boil, for about 6-8 minutes.
Reduce the heat to medium-low and continue to cook for another one to two minutes until the milk is the consistency of a thick syrup. Turn off the heat for the next step.
Beat your eggs in a medium-sized mixing bowl.
Begin to temper your eggs by pouring 1 cup of the hot milk mixture into the eggs, whisking constantly.
Return the saucepan to cook on medium heat. Pour the egg mixture slowly into the saucepan, stirring constantly, and continue to cook for 2-3 minutes or until the mixture is a very thick custard consistency (the custard should coat the back of your spoon and not run off). Remove from the heat.
Whisk the butter and vanilla extract into the custard mixture until smooth. Allow the custard to cool for 10 minutes, occasionally stirring to prevent a film from forming.
ASSEMBLE PIE:
While the custard cools, remove the pie crust from the refrigerator and slice two bananas to place into the bottom of the pie crust.
Pour the cooled custard over the top of the bananas in the pie crust. Use a spatula or frosting knife to smooth out the top.
Next, spread the Cool Whip over the top of the custard layer.
CHILL PIE:
Place the banana pie in the refrigerator and chill for at least 3-4 hours to allow the custard to fully set or overnight.
When ready to serve, garnish with slices of the remaining banana.
Slice and serve.
Notes
Troubleshooting Tips:
If your custard becomes runny, you didn’t cook your custard long enough. Make sure the custard is very thick before allowing it to cool.
Fattier milk helps with custard thickness. Skim milk may end up with a runny filling.
Brushing lemon juice on your bananas will prevent the bananas from browning in the leftover pie.