In a medium saucepan, whisk together egg yolks, granulated sugar, cornstarch, vanilla bean paste, and salt until pale and smooth.

Warm whole milk in a separate saucepan or in the microwave until just warm (do not boil).

Slowly stream the warm milk into the egg mixture while whisking constantly to temper the yolks.

Return the mixture to the saucepan and cook over low heat. Whisk continuously until the custard thickens and begins to bubble, about 10–15 minutes.

Remove from heat. Strain the custard through a fine-mesh sieve into a clean bowl to remove any bits.

Stir in unsalted butter until melted and incorporated. Press plastic wrap directly onto the surface and chill until completely cold.

When ready to assemble, pour heavy cream, powdered sugar, and vanilla extract into a chilled mixing bowl.

Whip on low speed to combine, then increase to medium-high until medium-stiff peaks form. Don’t overwhip.

Reserve about half of the whipped cream for topping. Fold the remaining whipped cream gently into the chilled pastry cream using a rubber spatula until uniform and light.

Slice ripe bananas just before assembling to avoid browning.

In individual cups or jars, place a layer of broken Nilla wafers to cover the bottom.

Spoon a scoop of the pudding mixture over the cookies.

Add a layer of sliced bananas.

Add another scoop of pudding to cover the bananas.

Top each cup with a dollop of the reserved whipped cream.

Chill the cups for at least 2 hours so the flavors meld and the wafers soften to the right texture. Before serving, garnish with extra Nilla wafers for crunch.