Slice bananas (into 1/4-3/8" slices) and set aside.
Add evaporated milk, egg yolks, flour & sugar to a saucepan. Whisk to incorporate and bring to simmer over medium to medium-high heat until thickened, continuing to whisk/stir.
Remove custard from heat and add vanilla. Give a quick stir to incorporate
Start layering banana pudding by covering the bottom of your chosen dish with Nilla wafer cookies followed by a layer of scattered bananas then pouring a layer of the custard.
Repeat this layering method until all custard is used then finish with a final layer of nilla wafers.
Crush a couple cookies and sprinkle on top to cover gaps left by whole Nilla wafer cookies.
Cover with plastic wrap or lid and refrigerate for a minimum of 6 hours or preferably overnight to allow cookies to soften