Combine 2 ripe bananas (saving the third one for later), 1/3 cup heavy cream, and 1/4 cup milk in a blender (or a medium bowl if you're using an immersion blender) and puree until totally smooth.
Once the mixture is completely smooth, add 1/2 cup granulated sugar, 2 tablespoons cornstarch, 1/2 teaspoon kosher salt, and 3 egg yolks and continue to blend until homogenous. Pour the mixture into a medium saucepan, and clean the blender canister (or medium bowl).
Bloom 1 tablespoon powdered gelatin by sprinkling it evenly across the surface of a small bowl filled with 2 tablespoons of cold water. The gelatin is bloomed when it is soft, about 2 minutes.
Whisk the contents of the pan (from the 2nd step) and heat over medium-low heat, whisking constantly. As the banana mixture heats up, it will thicken. Bring to a boil and, once it's at boiling point, continue to whisk vigorously for about 2 minutes to fully cook out the starch. The mixture will resemble thick glue, bordering on cement, with a color to match.
Transfer the contents of the pan back into your blender (or medium bowl, if using an immersion blender). Add the bloomed gelatin (from the 3rd step) and 3 tablespoons butter and blend until the mixture is smooth and even. Add 1/2 teaspoon yellow food coloring until it is a bright, artificial banana yellow.
Transfer the banana mixture to a heatproof container, and let cool in the fridge for as long as it takes to cool completely, about 30 to 60 minutes.
When the banana mixture has cooled, make whipped cream by combining 3/4 cup heavy cream with 1 cup confectioner's sugar in a freestanding electric mixer fitted with a whisk attachment. Whisk until the cream and sugar combine to create medium-soft peaks (when you pull the whisk away from the whipped cream, the mounds of cream should hold their shape softly — DO NOT OVERMIX or you'll end up with butter!). Add the cold banana mixture (from the 6th step) to the whipped cream and slowly whisk until evenly colored and homogenous — the mixture should turn into a pale yellow.
Once the banana cream is ready, pour half the mixture into the chocolate pie shell. Cover it with a layer of sliced bananas (from your remaining banana), then cover the bananas with the remaining banana cream. The pie should be stored in the fridge and eaten within a day.