Mix together the ice cold water, vanilla pudding mix, and sweetened condensed milk until thick, about 10 minutes on medium-high speed. **NOTE: The mixture should look like pudding**. Finally, add in vanilla extract and mix for another minute or so.
Next, whip the heavy cream until soft peaks form (or if using Cool Whip, you can skip this step!). Gently fold in the homemade whipped cream (or Cool Whip) into the pudding mixture using a rubber spatula until, well incorporated.
Meanwhile, begin melting the peanut butter in small pot on medium-high heat, whisking frequently until smooth and 'liquidy' in consistency.
In a trifle bowl (or your favorite dish), layer vanilla wafers, sliced bananas, pudding mixture, and drizzle peanut butter; repeat layering until all ingredients have been used. Garnish top with remaining vanilla wafers (some crushed, some whole), whipped cream, and a light peanut butter drizzle. Refrigerate for at least 2-3 hours before serving. Best if chilled overnight.