In a mixing bowl, combine crushed vanilla wafers and melted butter, stirring until the mixture resembles wet sand. Firmly press into the bottom of a lined 12-cup muffin tin.

Using an electric mixer, beat softened cream cheese on medium speed until smooth and fluffy, about 2-3 minutes. Gradually add sweetened condensed milk, mashed ripe banana, and vanilla extract, mixing thoroughly. Carefully fold in whipped topping.

Place a thin slice of banana on top of each crust. Spoon or pipe the cheesecake filling over the banana slices, smoothing the tops with a spatula.

Refrigerate the cheesecakes for 1-2 hours until set, or freeze them for 30 minutes for a firmer texture.

Before serving, top each mini cheesecake with a swirl of additional whipped topping and garnish with mini vanilla wafer. Add banana slices just before serving.