For the vanilla custard: Whisk 1/2 cup half-and-half with the cornstarch in a heatproof medium bowl until smooth. Whisk in the eggs and set aside.
In a heavy, medium saucepan, heat the remaining 1 1/2 cups half-and-half, the granulated sugar and vanilla beans over medium-low heat until a thin skin forms on the top, about 8 minutes.
Slowly whisk the hot half-and-half mixture into the egg mixture to temper it. Return the mixture to the saucepan and cook, stirring constantly with a rubber spatula, until it is just thick enough to coat the back of a wooden spoon, about 10 minutes. Remove from the heat and add the butter, 1 tablespoon at a time, stirring until combined. Stir in the vanilla extract.
Pour the custard into a clean bowl and press plastic wrap directly on the surface to prevent a skin from forming. Refrigerate for at least 4 hours, or overnight.
For the whipped cream: Beat the heavy cream and the confectioners' sugar in a medium bowl until soft peaks form.
For the shooters: Put 1 teaspoon wafer cookies in the bottom of each shot glass. Top with 1 teaspoon vanilla custard and a few pieces of chopped banana. Top with 1/2 teaspoon cookies and 1/2 teaspoon custard. Add a dollop of whipped cream and garnish with crushed cookies or chopped banana. Serve cold.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.