Crust: crush the vanilla wafers into crumbs and mix with the melted butter and sugar. Press into a lined baking dish. Bake at 350F for 9 minutes, then let cool completely.
Filling: whisk the instant banana pudding with the cold whole milk until it starts to thicken. In another bowl, beat the softened cream cheese until smooth, then fold in the pudding until combined.
Layer the sliced bananas over the cooled crust, then spread the pudding filling on top.
Whipped cream: beat the heavy cream, powdered sugar, and vanilla to stiff peaks. Spread over the filling.
Garnish with the reserved vanilla wafers and banana slices. Chill to set – it works best overnight – then slice into bars.