Preheat oven to 325°. Place prepared pastry into a pie plate. Cover pastry with a sheet of parchment paper, then add a layer of pie weights, rice, or dried beans. Blind-bake for 20 minutes or until lightly browned, then let cool before removing parchment and weights.
In a saucepan, combine milk, sugar, and salt. Whisk over medium heat until sugar has dissolved, then bring to a gentle simmer. Working quickly, whisk egg yolks and cornstarch together in a heatproof bowl until smooth. Slowly temper, adding a small amount of the heated milk and whisking constantly until eggs have come up to warm room temperature to avoid scrambling. Once eggs are tempered, add egg mixture into the pan of warmed milk. Whisking constantly, cook until custard is thickened and big bubbles begin bursting at the surface, 1–2 minutes. Remove from heat and whisk in vanilla extract. Place a piece of plastic wrap directly on top of the custard to prevent it from forming a skin and allow to cool.
In the meantime, slice 2 bananas and place into the bottom of the cooled pie shell. Top with cooled filling and chill, using a piece of plastic wrap to prevent a skin from forming. Refrigerate for at least 2 hours and up to 1 day before serving. Top with whipped cream to serve