Whisk together sugar, cornstarch, salt, milk, vanilla, banana extract and egg yolks in a saucepan over medium heat.
Cook until bubbles form and the mixture starts to thicken (about 6-8 minutes.) Remove from heat.
Pour pudding into a heat safe bowl and cool to room temperture. Move to fridge to finish chilling for at least 2-3 hours (or until fully set).
To Make the Cupcakes
Preheat oven to 350°F and prep a muffin tin with cupcake liners.
Using a hand or standing mixer, beat together cupcake ingredients until well combined.
Scoop batter into the prepared muffin tin so that each cup is 3/4 full. Bake for 19-20 minutes.
Cool completely before frosting.
To Make the Cinnamon Frosting
Using a standing mixer, beat together the butter, powdered sugar, heavy whipping cream, and vanilla extraxt until you have a smooth consistency and stiff peaks form.
Scoop frosting into the piping bag, if desired, for easy decorating.
To Decorate
Scoop a heaping Tablespoon of banana pudding onto each cupcake and spread evenly.
Pipe a generous dollop of frosting on top of the pudding.
Sprinkle with cinnamon and top with a vanilla wafer cookie.