Preheat the oven to 350 degrees F. Spray a 9-inch pie plate with cooking spray.
In a food processor, process graham crackers until finely ground. Add butter and 1 tablespoon of water, and process until the crumb clumps together. Press crumb mixture into bottom of pie plate and about 1/2-inch up the sides. Bake in the oven for 10 minutes, then let cool.
In the meantime, make the filling. Put the gelatin in a small bowl; add 3 tablespoons of boiling water and stir until gelatin is dissolved.
In a medium saucepan, whisk together 1/3 cup of sugar and the flour. Add the milk and cook over medium heat, whisking constantly, until the flour and sugar dissolve and the mixture comes to a gentle boil. In a medium bowl, lightly beat the egg yolks. Ladle about 1/2 cup of the warm milk mixture into the eggs yolks to bring the temperature of the egg yolks up gradually while whisking. Add the tempered eggs to the hot milk mixture in the saucepan and continue to cook over medium heat, stirring constantly, until the mixture returns to a gentle boil and has thickened, about 5 minutes. Stir in the vanilla extract and gelatin. Set aside to cool slightly.
Arrange the sliced bananas on the graham cracker crust and pour the pudding on top. Place in the refrigerator until the pudding has set, about 3 hours.
Whip the cream with an electric beater. When it is about halfway done, add 1/2 teaspoon of sugar, then continue whipping until fully whipped. Put the whipped cream in a plastic bag, concentrating it in 1 corner of the bag. Snip that corner off the bag and squeeze the whipped cream out of the bag in a decorative pattern around the pie.