In a large mixing bowl, beat the sweetened condensed milk with an electric mixer while slowing streaming in the water. Add the pudding mix and beat until thoroughly mixed in. Cover pudding and refrigerate for at least 4 hours or overnight so it can can thicken and set up.
Beat the heavy whipping cream with an electric mixer until stiff peaks from. Fold the whipped cream and chilled pudding together until there are no more streaks.
Assemble the pudding in either a large bowl, trifle dish, baking pan, or individual dishes. Layer the ingredients by first adding a layer of Nilla Wafers, followed by sliced bananas, and then pudding. Repeat layers until you reach the top of your dish(es).
Cover tightly with plastic wrap and place the assembled dessert in the fridge for 4-8 hours. Top with additional bananas and Nilla wafers (optional) and serve.