Step 1: In a large mixing bowl, whisk together the cold whole milk and both boxes of instant vanilla pudding mix for 2 minutes until well combined.
Step 2: Stir in the can of sweetened condensed milk and whisk until the mixture is smooth. Let the pudding mixture sit for 5 minutes to thicken.
Step 3: In a separate, chilled bowl (using a stand mixer or hand mixer), beat the very cold heavy whipping cream, powdered sugar, and vanilla extract until stiff peaks form. Be careful not to over-beat and turn it into butter.
Step 4: Gently fold about two-thirds of the whipped cream into the thickened pudding mixture until just combined. This creates a light and airy peanut butter-infused pudding.
Step 5: To assemble, place a single layer of Nutter Butter cookies at the bottom of a 9x13-inch baking dish or a large trifle bowl. Break some cookies as needed to fill in any gaps.
Step 6: Arrange a thick layer of sliced bananas evenly over the Nutter Butter cookies.
Step 7: Carefully pour half of the pudding mixture over the bananas, spreading it gently to cover them completely.
Step 8: Repeat the layers: add another layer of Nutter Butter cookies, followed by the remaining sliced bananas, and then the rest of the pudding mixture.
Step 9: Spread the remaining one-third of the whipped cream evenly over the top layer of pudding. For garnish, crush a few extra Nutter Butter cookies and sprinkle them over the whipped cream.
Step 10: Cover the dish tightly with plastic wrap and refrigerate for at least 4 hours, or preferably overnight, to allow the cookies to soften and the flavors to meld beautifully.