For the filling:
¼ cup banana liqueur
3½ tsp. unflavored gelatin
1 vanilla bean, split
2¾ cups milk
4 large egg yolks
¾ cup sugar
3 tbsp. cornstarch
1 (9-inch) blind-baked pie crust*
3 oz. bittersweet chocolate, chopped and melted
¼ cup creamy peanut butter
2-3 bananas, sliced
Juice of 1 lemon (optional)
1¼ cups heavy cream
6 tbsp. confectioners’ sugar
1 tsp. vanilla extract
1 banana, sliced
Hot fudge sauce
Honey roasted peanuts, coarsely chopped
To assemble the pie, brush the inside of the pie crust with a thin layer of the melted chocolate. (This will prevent the crust from getting soggy). Transfer to the refrigerator to chill for about 20 minutes. Spread the peanut butter over the bottom of the pie crust in an even layer. Cover with a single layer of banana slices. (If desired, brush the banana slices very lightly with lemon juice to help prevent browning. This is purely aesthetic and not essential to the taste of the pie.)
To make the filling, pour the banana liqueur into a small microwave-safe bowl. Sprinkle the gelatin over the top and let it soften at least 5 minutes. Microwave for 10 seconds to dissolve the gelatin. Combine the vanilla bean pod and the milk in a small saucepan and bring to a boil. Remove from the heat, cover, and let steep while preparing the yolk mixture.
In a medium bowl, combine the egg yolks and sugar. Whisk thoroughly until the mixture lightens in color to a lemon yellow, about 5 minutes. Whisk in the cornstarch. Very slowly add the warm milk mixture to the bowl with the egg yolks, whisking constantly to avoid curdling. Return the mixture to the saucepan and heat over medium-high heat, whisking constantly, until the mixture has thickened slightly and reads 170-175˚ F on an instant-read thermometer. Remove the mixture from the heat and whisk in the gelatin mixture. Let the filling cool completely, about 30 minutes.
Spread the pastry cream into the pie shell and smooth the top with a spatula. Top with a second layer of banana slices, again brushing with the lemon juice if desired. Cover with a piece of plastic wrap directly on the surface of the pastry cream and refrigerate.
Just before serving, combine the heavy cream and confectioners’ sugar in the bowl of an electric mixer. Whip on medium-high speed with the whisk attachment until stiff peaks form, taking care not to over-beat. Blend in the vanilla. Spread the whipped cream on top of the pie. Top with additional banana slices. Slice the pie and place on dessert plates. Drizzle each serving with warm hot fudge sauce and sprinkle with chopped peanuts. Serve immediately.
*To blind-bake a pie crust, preheat the oven to 400˚ F. Roll pie dough out on a lightly floured surface to a 12-inch disc. Place it in a 9-inch pie plate, trimming away the excess and creating decorative edges as desired. Prick the bottom and sides of the crust with the tines of a fork. Line the crust with a piece of aluminum foil or parchment paper and fill with baking beads. (If you don’t have baking beads, dried beans or rice also work.) Bake 15-20 minutes. Remove the baking beads and foil and bake about 5-10 minutes more, until light golden. Transfer to a wire rack and let cool.