Classic Banana Cream Pie

Place a rack in middle of oven; preheat oven to 350°. Mix 1¾ cups (210 g) finely crushed graham crackers (about 15), ½ cup (1 stick) unsalted butter, melted, slightly cooled, ¼ cup (50 g) granulated sugar, and ½ tsp. Diamond Crystal or ¼ tsp. Morton kosher salt in a large bowl until mixture looks like wet sand.

Transfer graham cracker mixture to pie dish and press evenly across bottom and up sides all the way to the edges with your hands or a flat-bottom glass until compact and smooth. Bake crust until set and fragrant, 12–15 minutes. Transfer to a wire rack and let cool.

Whisk ¾ cup (150 g) granulated sugar, ½ cup (62 g) all-purpose flour, ½ tsp. Diamond Crystal or ¼ tsp. Morton kosher salt, and 2½ cups whole milk in a medium saucepan to combine. Cook over medium heat, whisking often, until simmering and sugar is dissolved, about 5 minutes. Remove from heat.

Whisk 3 large egg yolks in a small bowl to blend. Gradually add 1 cup hot milk mixture, whisking vigorously as you pour. (This will ensure that the yolks don’t cook.) Whisking constantly, add egg mixture remaining milk mixture in saucepan; scrape out bowl with a rubber spatula to get it all. Cook over medium heat, whisking constantly, until thick and a few bubbles are breaking on the surface, about 4 minutes. Continue to cook, whisking constantly and adjusting heat as needed to ensure pastry cream does not boil, 2 minutes more. Remove from heat and add 4 Tbsp. chilled unsalted butter, cut into ½" pieces, and 2 tsp. vanilla extract; whisk until smooth.

Strain pastry cream through a fine-mesh sieve into a medium bowl. Cover with plastic wrap, pressing directly onto surface to prevent a skin from forming, and chill until room temperature, 30–40 minutes.

Shingle 2–3 bananas, sliced ¼" thick, across bottom of crust. (Using 2 bananas if you want a thinner layer, 3 if you like more bananas.) Spoon pastry cream over bananas (if it has become firm, whisk gently to loosen); smooth with an offset spatula or a spoon. Cover with plastic wrap and chill until set, at least 4 hours.

Just before serving, using an electric mixer, beat 1 cup heavy cream, ¼ cup (28 g) powdered sugar, sifted, 2 tsp. bourbon (if using), remaining 1 tsp. vanilla extract, and remaining ½ tsp. Diamond Crystal or ¼ tsp. Morton kosher salt in a chilled small bowl, starting on low speed and working up to medium-high, until soft peaks form, about 2 minutes. Top pie with whipped cream and sprinkle with flaky sea salt. Do ahead: Pie (without whipped cream) can be made 1 day ahead. Keep chilled.