In a saucepan, bring half and half to a boil with vanilla paste and banana extract.
In a mixing bowl, combine sugar, cornstarch, and salt.
Add egg yolks to the dry mixture and whisk until fully incorporated.
Slowly pour the hot cream mixture into the egg mixture, stirring constantly to temper.
Return the mixture to the pot over medium heat.
Bring to a boil, stirring constantly.
Once boiling, add butter and continue stirring for 1 more minute. Remove from heat.
Strain into a storage container.
Cover with plastic wrap directly on the surface to prevent a skin from forming.
Chill for at least 4 hours or overnight.
Add a layer of custard to the bottom of a glass.
Top with crumbled Nilla wafers and fresh sliced bananas.
Repeat layers until full.
Finish with whipped cream and a Nilla wafer on top.
