In a mixing bowl, combine vanilla wafer crumbs, granulated sugar, melted unsalted butter, kosher salt, and finely chopped pistachios. Mix well, then press the mixture into the bottom and up the sides of a pie plate. Freeze for 10 minutes while you preheat your oven to 350°F (175°C).

Place the crust in the preheated oven and bake for 15 minutes, or until lightly golden. Allow it to cool completely before filling.

In a separate bowl, whisk together the egg yolks and cornstarch until smooth. Heat dark brown sugar and a splash of water over medium heat until dissolved.

Bring it to a gentle boil until thickened, then gradually whisk in the heavy cream and whole milk. Slowly pour a bit of the hot mixture into the egg yolks to temper them, then return it to the saucepan, cooking until thick, stirring constantly.

Pour half of the banana slices into the cooled crust, followed by the warm butterscotch pudding. Smooth the pudding out, then layer the remaining banana slices on top.

Allow the pie to cool for 30 minutes at room temperature, then chill in the refrigerator for at least 4 hours to set fully.

In a mixing bowl, beat the crème fraîche and heavy cream together until medium-stiff peaks form. Sweeten the mixture with powdered sugar and add in dark rum or vanilla extract for extra flavor.

Spread the whipped cream on top of the pie and garnish with chopped pistachios.

When ready to enjoy, slice the pie directly from the cold refrigerator and serve.

For an added crunch and flair, sprinkle extra pistachios over the whipped topping before serving.