Banana Cream Pie

Place a rack in middle of oven; preheat oven to 350°. Whisk 2½ cups graham cracker crumbs and ⅓ cup (67 g) sugar in a large bowl to combine. Add ¼ cup mashed banana and mix with a rubber spatula to combine. Pour in 4 Tbsp. unsalted butter, melted, and mix until crust mixture is evenly moistened.

Press mixture firmly and evenly into the bottom and up the sides of a 9½"-diameter glass or metal pie plate. Chill until firm, about 30 minutes.

Bake crust until set and golden, 14–16 minutes. Transfer to a wire rack and let cool to room temperature.

Whisk ½ cup (100 g) sugar, ⅓ cup cornstarch, and ¼ tsp. kosher salt in a heavy medium saucepan to combine. Slowly pour in 1½ cups heavy cream and 1½ cups whole milk, whisking constantly until combined. Add 3 large egg yolks one at a time, whisking vigorously until mixture is smooth after each addition. Scrape in seeds from ½ vanilla bean, split lengthwise, then add pod.

Place saucepan over medium-high heat and cook custard, whisking constantly and making sure to get into corners of pan, until bubbling and thickened, 5–7 minutes. Remove from heat and whisk in 2 Tbsp. unsalted butter and 1 tsp. vanilla extract; remove and discard vanilla pod. Scrape custard into a medium bowl and let cool, whisking occasionally, about 1 hour.

Stir custard to loosen if needed. Spread 1 cup custard over bottom of crust. Layer with half of 5 ripe bananas, sliced crosswise ¼" thick. Spread another 1 cup custard over bananas, making sure to cover bananas completely. Repeat layering with remaining bananas and custard. Press a layer of plastic wrap directly on the surface of the pie. Chill until custard is set and crust is slightly softened, at least 8 hours and up to 1 day.

Cut pie into wedges and garnish with whipped cream and more sliced bananas if desired. Do ahead: Pie shell can be baked 2 days ahead of time; wrap well and keep refrigerated or freeze for up to 3 months. Banana Cream Pie can be assembled, without whipped topping, up to 2 days ahead of time; keep chilled.