In a medium saucepan, combine sugar, cornstarch and salt. Gradually whisk in evaporated milk, until sugar and cornstarch begin to dissolve.

Whisk in eggs and add butter. Cook over medium heat, stirring constantly, until the mixture begins to thicken. Reduce heat to low, simmer and cook for 1 minute, stirring constantly.

Remove from heat. Stir in vanilla extract. Allow pudding to cool.

Line the bottom of six 1/2 pint jars with 3 wafers each. Evenly divided 1/2 of the banana slices over the wafers. Evenly spoon 1/2 of the pudding over bananas. Repeat layers ending with pudding.

Refrigerate trifles for a couple of hours. Just before serving, top with whipped cream and a Nilla wafer for garnish.