In a medium saucepan, whisk together 1 cup of sugar, 1/3 cup of flour, and a pinch of salt until well blended. Gradually whisk in 4 cups of milk over medium heat, stirring continuously. Cook for about 5-7 minutes until it starts to thicken and bubble vigorously.

Once bubbling, reduce the heat to low and let the mixture simmer for an additional 2 minutes while stirring constantly. Remove from heat and allow it to cool slightly.

In a separate bowl, whisk together 4 egg yolks. Gradually add a small amount of the hot custard mixture into the bowl while whisking vigorously. Pour the tempered egg mixture back into the saucepan with the remaining custard, stirring continuously. Return to low heat and cook for about 2 minutes until gently boiling.

Remove the custard from heat and stir in 1 tablespoon of vanilla extract. Allow the custard to cool for 15 minutes, stirring occasionally to prevent a skin from forming.

In an ungreased 8-inch square baking pan, layer half of the vanilla wafers at the bottom, followed by half of the sliced bananas then pour half of the cooled custard mixture on top. Repeat layering, ending with the remaining custard.

Cover the pudding with plastic wrap and let it chill in the refrigerator for at least 4 hours, preferably overnight.

Before serving, crush some additional vanilla wafers and sprinkle them on top for a delightful crunch.