For the pastry cream:
2 cups half and half
½ cup sugar, divided
Pinch of salt
5 large egg yolks
3 tablespoons cornstarch
4 tablespoons cold unsalted butter, cut into 4 pieces
1½ teaspoons vanilla extract
For the cupcakes:
3 cups cake flour
1 tablespoon baking powder
½ teaspoon salt
1 vanilla bean, split lengthwise
1 cup (2 sticks) unsalted butter, at room temperature
2 cups sugar
5 large eggs, at room temperature
1¼ cups buttermilk, at room temperature
1 tablespoon vanilla extract
For the whipped cream:
1¾ cup heavy cream
6 tablespoons confectioners’ sugar
2 teaspoons vanilla extract
60 banana slices (about 3 bananas), plus more for topping if desired
Half batch pie dough
1 large egg beaten with 1 tablespoon water
Start by making the pastry cream. Heat the half and half, 6 tablespoons of sugar and the salt in a saucepan over medium-high heat until shimmering, stirring occasionally to dissolve the sugar. Meanwhile, in a medium bowl, whisk together the egg yolks and remaining 2 tablespoons of sugar for about 15 seconds, until the mixture is creamy and the sugar has started to dissolve. Add the cornstarch and continue whisking another 30 seconds, until the mixture is pale yellow and thick. Slowly pour in the simmering half and half, whisking constantly, to temper the eggs. Return the mixture to the saucepan over medium heat, whisking constantly for about 30 seconds until a few bubbles have burst on the surface and the mixture is thick and glossy. Remove from heat and whisk in the butter and vanilla. Place a fine mesh strainer over a medium bowl and strain the pastry cream. Place plastic wrap directly on the surface and refrigerate until cold and set, at least 3 hours and up to 2 days.
To make the cupcakes, heat oven to 350º. Line cupcake pans with paper liners and set aside. In a medium bowl, whisk together the cake flour, baking powder and salt. In the bowl of an electric mixer fitted with the paddle attachment, beat together the butter and seeds from the vanilla bean on medium-high for 3 minutes, until the mixture is light and creamy. Scrape down the sides of the bowl and continue beating an additional minute.
Add the sugar, ¼ cup at a time, beating 1 minute after each addition. Add the eggs one at a time and beat until incorporated, scraping down the sides of the bowl as needed. Combine the buttermilk and vanilla extract. Reduce mixer speed to low and alternately add the dry ingredients and wet ingredients, starting and ending with the dry. Mix until just incorporated, then scrape down the sides of the bowl and mix for another 15 seconds.
Divide the batter between the prepared liners, filling each about ⅔ full. I like to use a large cookie scoop. Bake for 18-22 minutes, or until a toothpick inserted in the center comes out clean. Allow to cool in the pans for 5-10 minutes before transferring to a cooling rack to cool completely. Repeat with remaining liners and batter.
To fill the cupcakes, remove the center using the cone method. Discard (snack on) the cones. Place a slice of banana inside of each cupcake. Add a spoonful of pastry cream and another slice of banana.
To make the frosting, combine the cream and confectioners’ sugar in the bowl of an electric mixer fitted with the whisk attachment. Whip on medium-high speed until stiff peaks form, taking care not to over-beat. (If you’re worried, you can always use the mixer until soft peaks form and then finish it off by hand.) Blend in the vanilla. Transfer the whipped cream to a pastry bag fitted with a star tip. Pipe a swirl of whipped cream onto each cupcake.
To finish, heat the oven to 400º. Line a baking sheet with a nonstick baking mat or parchment paper. Roll out the pie dough on a lightly floured surface and cut small decorative rounds with a cookie cutter. Transfer to the prepared baking sheet and lightly brush with egg wash. Bake for about 15 minutes, or until light golden brown. Allow to cool completely. Just before serving, top cupcakes with a round of pie crust and another slice of banana.