Whisk together the sugar, cornstarch, egg yolks and milk in a saucepan. Cook over medium heat while stirring constantly until the mixture becomes smooth and thick.

Remove the saucepan from the heat. Stir in the butter and vanilla extract. Mix until fully combined. Let the pudding cool slightly before assembling the dessert.

In a mixing bowl, whip the heavy cream with powdered sugar until soft peaks form. The whipped cream should be light, fluffy and easy to spread.

Peel the bananas and slice them into even rounds. Choose ripe bananas with yellow skins and a few brown spots for the sweetest flavor.

Place vanilla wafer cookies in the bottom of the serving dish. Add a layer of banana slices. Spoon some warm pudding over the top and spread evenly.

Continue layering cookies, bananas and pudding until all the ingredients are used. Finish with a smooth layer of pudding covering the top completely.

Spread the whipped cream evenly over the pudding. Use a spatula to create soft swirls. Garnish with extra banana slices if desired.

Cover the dish with plastic wrap and refrigerate for at least four hours. This allows the flavors to blend and softens the cookies perfectly.