Prepare the Crust:Preheat the oven to 375°F (190°C). Roll out your crust and fit it into a pie dish. Line with parchment paper, add pie weights, and blind bake for 15 minutes. Remove weights and bake for another 10–15 minutes until golden. Cool completely.
Make the Custard Filling: In a medium saucepan, whisk together sugar, cornstarch, and salt. Gradually whisk in milk. Cook over medium heat, stirring constantly, until thick and bubbly (5–8 minutes).
Temper the egg yolks by slowly adding some hot milk mixture to them while whisking. Pour yolks back into the saucepan and cook 2–3 more minutes until thick. Remove from heat and stir in butter and vanilla. Cover the surface with plastic wrap and cool to room temperature.
Layer the Bananas: Slice bananas. Arrange half on the cooled crust. Spread half the custard over bananas. Repeat with remaining bananas and custard, smoothing the top.
Whip the Cream:In a chilled bowl, beat heavy cream, powdered sugar, and vanilla until soft peaks form. Spread or pipe over the pie.
Chill and Serve: Refrigerate for at least 4 hours (or overnight) until set. Slice and serve chilled.