Whisk the flour, sugar, and salt in a bowl, then toss in the cold butter cubes and cut them into the dry mixture with a pastry blender or two knives until the pieces are pea-sized. The mix should still show small butter bits, because those cold pockets help create flaky layers in the oven.

Stir in the cold water with a spatula, then use your hands just enough to bring the dough into a ball, adding more water a teaspoon at a time only if it will not hold together. Stop as soon as the dough gathers, since overworking it can make the crust tougher instead of tender and crisp.

Press the dough into a disk, wrap it well, and chill it in the refrigerator for at least 1 hour and up to 5 days. The dough should feel firm and cool, which helps control shrinkage when you roll and bake it later.

Let the chilled dough sit at room temperature for 5 minutes, then roll it on a lightly floured surface into a rough 13-inch circle about 1/4-inch thick. If the dough softens too fast or sticks, it needs a brief chill so it stays easy to lift and shape.

Drape the rolled dough into a 9-inch pie dish, then fold and crimp the edges as you like without stretching the pastry. Lowering it in gently helps prevent tears, and avoiding stretch keeps the crust from shrinking back in the oven.

Freeze the shaped crust for 30 minutes while the oven preheats to 425 °F. The shell should feel firm and cold, which helps the edges hold their shape during blind baking.

Line the frozen crust with greased foil or parchment and fill it completely with pie weights, dry beans, or rice. The liner should cover the dough snugly and the weights should reach the top so the sides stay supported.

Bake for 20 to 25 minutes until the edges are golden, then remove the liner and weights and let the crust continue baking for 5 to 10 minutes more until lightly browned all over. The finished shell should look evenly baked and feel crisp, with no pale or damp-looking patch in the center.

Warm the milk and sugar in a medium saucepan over medium heat while whisking the egg yolks and cornstarch together in a separate bowl. When the milk steams and tiny bubbles appear around the edge, it is hot enough to temper the yolks.

Pour the hot milk mixture slowly into the yolk mixture while whisking, then return everything to the saucepan and cook over medium heat, whisking constantly. The custard will go from loose to noticeably thick, and it should stay smooth as it cooks.

Take the pan off the heat once thickened, then stir in the vanilla and butter until fully blended. The finished pudding should look glossy and rich and coat the back of a spoon instead of running off quickly.

Let the pudding cool to room temperature, stirring from time to time as it cools. It should still be creamy and spreadable, not hot, before it goes anywhere near the crust or bananas.

Heat the heavy whipping cream in the microwave until steaming, then pour it over the chopped chocolate in a medium bowl and leave it alone for 5 minutes. The chocolate should soften quietly in the hot cream instead of being rushed with immediate stirring.

Stir the mixture until the ganache turns smooth and uniform. It should look glossy with no unmelted bits or oily streaks.

Beat the heavy whipping cream until it begins to thicken, then add the vanilla and sugar and continue beating to medium peaks. The whipped cream should hold soft, curved peaks that stand up but still look smooth and spreadable.

Spread the ganache across the bottom of the cooled pie crust, arrange the sliced banana in an even layer, then spoon the cooled vanilla pudding over the fruit and smooth it to the edges before topping with the whipped cream. Each layer should sit neatly in place, and the custard should fully cover the bananas so they are sealed from the air.

Chill the finished pie for at least 2 hours before serving, then add additional chopped chocolate or sliced bananas, for topping (optional), just before slicing if you like. The filling should feel set and slice cleanly rather than slumping when the knife goes in.