Banana cream pie

Crust
2 1/2 cups graham cracker crumbs
1/3 cup sugar
1/4 cup mashed banana
1/4 cup (1/2 stick) unsalted butter, melted

Filling
1/2 cup sugar
1/3 cup cornstarch
1/4 teaspoon salt
1 1/2 cups whipping cream
1 1/2 cups whole milk
3 large egg yolks
1/2 vanilla bean, split lengthwise
2 tablespoons (1/4 stick) unsalted butter
1 teaspoon vanilla extract
5 ripe bananas peeled, cut crosswise into 1/4-inch-thick slices

For crust:
Preheat oven to 350°F. Stir graham cracker crumbs, sugar, and mashed banana in large bowl to blend. Add unsalted butter and stir to moisten evenly. Press onto bottom and up sides of 10-inch-diameter glass pie dish. Chill until firm, about 30 minutes. Bake crust until set and pale golden, about 15 minutes. Cool completely.

For filling:
Whisk sugar, cornstarch, and salt in heavy medium saucepan to blend.
Gradually whisk in whipping cream and whole milk, then egg yolks.
Scrape in seeds from vanilla bean; add vanilla bean.
Whisk over medium-high heat until custard thickens and boils, about 6 minutes. Remove from heat.
Whisk in unsalted butter and vanilla extract. Discard vanilla bean.
Transfer custard to large bowl; cool completely, whisking occasionally, about 1 hour.

For pie:
Spread 1 cup custard over bottom of prepared crust.
Top with half of sliced bananas, then 1 cup custard, covering bananas completely.
Repeat layering with remaining bananas and remaining custard.
Chill banana cream pie until filling is set and crust softens slightly, at least 8 hours and up to 1 day.
Top the pie with whipped cream, if desired.