Heat oven to 375 degrees F, arrange rack in upper third, and place a baking sheet on rack while oven heats.
Meanwhile, roll dough on a lightly floured surface to a 12-inch diameter circle approximately 1/8-inch thick. Transfer dough to a 9 1/2-inch pie dish and trim edges so there is a 1/2-inch overhang. Use excess dough to press crust into pie plate
. Fold edge of crust back on itself and press, as desired, into a decorative crust. (Can be made 2 days ahead and kept covered in refrigerator until ready to use.)
Pierce bottom of crust all over with a fork. Line pie with aluminum foil so it overhangs slightly and covers edges of pie crust
and fill with uncooked rice
, dried beans
, or baking weights. Place pie dish on baking sheet and bake until crust is set and edges are slightly puffed up, about 25 minutes.
Gather foil together and remove along with weights. Continue to bake crust until it is thoroughly golden, about 15 minutes. Remove to a wire rack and let cool a few minutes before filling.
1 banana and place in a blender
with milk, egg yolks, cornstarch, sugar, vanilla, and salt and process until smooth. Pour into a small saucepan
, bring to a simmer
over medium heat and cook, stirring constantly until mixture bubbles and is thick, about 7 to 8 minutes. Remove from heat and stir in butter, a few pieces at a time, until melted. Set aside to cool slightly.
Pour in filling into the pie shell and evenly smooth with a spatula
. Slice remaining 3 bananas into 1/2-inch pieces and arrange on top of custard
. Smooth whipped cream over top, loosely cover in plastic, and set in refrigerator until cool and set, at least 3 hours.