In a medium mixing bowl, combine the crushed vanilla wafers and melted butter until the mixture resembles wet sand. Press into the bottom of a lined 12-cup muffin tin to create a firm crust.

In a large mixing bowl, beat the cream cheese on medium speed until smooth. Gradually add the sweetened condensed milk, mashed banana, and vanilla extract. Gently fold in the whipped topping.

Place a banana slice on each crust, then fill each cup with the cheesecake mixture, smoothing the tops.

Cover the muffin tin with plastic wrap and refrigerate for 1-2 hours, or freeze for 30 minutes if short on time.

Remove cheesecakes from the muffin tin, top with whipped topping and a mini vanilla wafer, and add banana slices just before serving.