In a large mixing bowl, combine the 2 cups of cold milk and 1 tsp of vanilla extract. Whisk together until combined. Gradually add in the 6.8 oz of instant vanilla pudding and whisk until thick and creamy, about 2 minutes.
Gently fold in the 14 oz of sweetened condensed milk into the pudding mixture. Adjust sweetness to taste and mix until smooth.
In a separate bowl, whip the 2 cups of heavy whipping cream until soft peaks form. Optionally, add 1 tbsp of powdered sugar.
Gently fold the whipped cream into the pudding mixture, maintaining the lightness of the cream.
In a 9x13-inch baking dish, layer the ingredients starting with vanilla wafers, then a layer of pudding, followed by slices of 2 bananas. Repeat until all ingredients are used, finishing with a layer of pudding.
Cover and refrigerate for at least 4 hours or overnight. Garnish with additional banana slices or crushed wafers before serving.