Lightly flour a smooth work surface and a rolling pin.
Take a chilled disk of dough out of the fridge. Give it a couple of firm squeezes just to say hello, then unwrap it and set it on the floured work surface.
Set the pin crosswise on the dough and press down firmly, making a nice deep channel across the full width of the disk. Turn the disk 180 degrees and repeat, making a second indentation, forming a plus sign.
Use your rolling pin to press down each of the wedges, turning the dough 45 degrees each time. This will give you the beginnings of a thick circle.
Now, rolling from the center outward and rotating the dough a quarter turn to maintain a circular shape, roll the dough out to a 13-inch circle with an even thickness of 1/4 inch.
Set your 9-inch (23-cm) pie pan alongside the circle of dough. Brush off any loose flour, carefully fold the dough circle in half, transfer it to the pan, and unfold.
At this point, the dough will be lying across rather than fitted into the pan. Now, without stretching the dough, set the dough down into the pan so that it is flush up against the sides and bottom. The best way to do this is to gingerly lift the dough and gently shift it around so that it settles into the pan bit by bit. Use a very light touch to help cozy it in.
To flute the edge, fold the overhang under to form a 1-inch wall that rests on the lip of the pan with the seam slightly below the pan’s top edge. Flute the edge of the crust at about 1-inch intervals, pressing from the inside with the knuckle of your index finger while supporting on the outside with the thumb and index fingers of your opposite hand.
Transfer the crust to the refrigerator to chill while you make your filling or to the freezer to prepare it for prebaking. Alternatively, at this point the crust can be covered tightly in plastic wrap and refrigerated for up to 3 days or double-wrapped and frozen for up to 2 months (defrost overnight in the refrigerator before filling and baking or prebaking, or at room temperature for 30 minutes).
To prebake the shell, chill the panned, fluted piecrust in the freezer until firm, 15 to 20 minutes.
Preheat the oven to 375 degrees F with the rack in the center. Line a rimmed baking sheet with parchment paper or foil. Cut an additional 13×13-inch square of parchment.
Set the pan on the lined baking sheet. Set the square of parchment in the pie shell and gently smooth it into place, pleating as needed to fit it up against the bottom and sides of the shell. The edges of the paper will project beyond the rim of the pan; just leave them standing straight up.
Fill the shell to the top with dried beans. Slide the baking sheet into the oven and bake the shell for 25 minutes.
Set out a wire rack and alongside it, a mixing bowl. Take the baking sheet out of the oven and set it on the rack; bring together the points of the parchment, and carefully lift out the beans and transfer them to the bowl.
Slide the baking sheet back into the oven and bake the crust another 10 minutes (until golden brown and fully baked–mine baked twice as long, an extra 20 minutes until the bottom of the crust was light golden). Cool completely on a wire rack.
To make the filling, combine the evaporated milk and whole milk in a medium saucepan and cook over medium heat, stirring occasionally, until steaming. Keep warm over very low heat.
Combine the sugar, cornstarch, salt, and nutmeg in a medium bowl and whisk together. Add the egg yolks and whisk until the mixture is smooth and pale. Immediately measure out 1 cup of the hot milk mixture and slowly add it to the yolk mixture, pouring in a thin stream and whisking constantly until combined.
Turn the heat under the saucepan back up to medium. Slowly add the tempered yolks to the saucepan, pouring in a thin stream and whisking constantly over medium heat. Continue cooking, whisking constantly, until the mixture thickens to a pudding consistency and a few large bubbles rise to the surface, 5 to 7 minutes. Once the bubbles appear, continue cooking the pudding, whisking constantly, for 2 more minutes.
Remove the saucepan from the heat and whisk in the butter, rum, vanilla, and banana extract, whisking until smooth. Set the pudding aside to cool for 5 minutes.
To assemble the pie, spoon half of the filling into the prepared shell and top with a single layer of 11 wafers, flat-sides up. Top each wafer with a banana slice, followed by another wafer flat-side down. Gently press the cookie sandwiches down into the filling. Spoon the remaining pudding into the pie shell and smooth the top.
Cover with plastic wrap, pressing onto the surface of the pudding, and chill overnight (at least 12 hours or up to 3 days) before slicing and serving. Serve cold, with whipped cream and a Nilla Wafer.