Place the pie crust dough in a 9-inch pie plate and flute the edges.
Refrigerate the pie crust, about 30 minutes.
Preheat the oven to 425 degrees F.
Line the pie crust with two layers of foil and fill with pie weights, dried beans, or uncooked rice.
Bake the pie crust on the lower oven rack until the edges are golden-brown, about 12-15 minutes.
Discard the foil and the weights, then bake the pie crust until the bottom is golden-brown, about 2-3 minutes.
Place the pie plate on a wire rack and let the pie crust cool.
In a saucepan, add the flour, the sugar, and the salt and stir to combine.
Stir the milk into the sugar mixture and mix well. Cook over medium-high heat until it has thickened and is bubbly.
Reduce the heat and cook the milk mixture, while stirring, about 2 minutes.
Transfer the saucepan from the heat.
In a medium bowl, lightly beat the egg yolks.
Stir a small amount of the milk mixture into the beaten egg yolks.
Add the egg-milk mixture to the milk mixture in the saucepan, transfer the pan back to the stovetop, and bring it to a gentle boil. Cook, stirring constantly, about 2 minutes.
Transfer the saucepan from the heat.
Gently stir the butter and the vanilla into the pie filling.
Pour the pie filling into a bowl, then press plastic wrap onto the surface of the pie filling and refrigerate, about 30 minutes.
Pour 1/2 of the chilled pie filling into the crust and top with 3 of the sliced bananas.
Pour the remaining pie filling over the banana slices.
Decorate with the whipped cream, as desired.
Chill the pie in the refrigerator for at least 6 hours and up to overnight.
Slice and serve the pie garnished with the extra banana slices.