In a large bowl, beat together the sweetened condensed milk and water until well combined - about 1 minute. Add the pudding mix and beat well. Cover and refrigerate for 3-4 hours to overnight. It is very important to allow the proper amount of time for the pudding mixture to set. It will be watery if you don't let it set up long enough.
In a large bowl, whip the heavy cream until stiff peaks form. Gently fold the whipped cream into the pudding mixture until no streaks of pudding remain.
To assemble dessert, use a 9x13 glass dish.
Arrange 1/2 of the vanilla wafers covering the bottom, overlapping if necessary. Next, layer 1/2 of the bananas, and 1/2 of the pudding mixture. Repeat once more, garnishing with additional wafers or wafer crumbs on the top layer. Cover tightly and allow to chill in the fridge for at least 4 hours - or up to 8 hours.
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Notes
The longer the banana pudding sits, the more likely the bananas are to brown. The best way to ensure the bananas won't turn brown is if you cover them completely with the pudding mixture so they aren't exposed to air.If you'd like to use a trifle dish, divide the vanilla wafers, the bananas and the pudding mixture into 3rds and layer three times instead of just two
Storage Instructions
Banana pudding tastes best within 24 hours of assembling but can be stored up to 2 days in the fridge. Keep it tightly covered. The bananas may brown slightly, but the flavor remains the same. To make ahead, prep the pudding and whipped cream separately, then assemble a few hours before serving. Freezing isn’t recommended—it changes the texture.