In a large mixing bowl, combine the 1 cup of whole milk and the instant vanilla pudding mix. Whisk them together until fully blended and smooth. Let it sit for about 5 minutes, allowing it to thicken.
Once the pudding has set, gently fold in the thawed whipped topping. Use a spatula to ensure the mixture remains light and fluffy. Be careful not to deflate the whipped topping.
Take the Oreos and crush them into smaller pieces. You can do this by placing them in a zip-top bag and using a rolling pin or simply using a food processor for a finer texture. Reserve about half a cup of crushed Oreos for topping.
Add the crushed Oreos to the pudding and whipped topping mixture. If you’re using miniature marshmallows, fold them in at this stage as well. Mix until everything is evenly combined.
Transfer the mixture into a serving dish or individual cups. Cover with plastic wrap and refrigerate for at least 1 hour, or until ready to serve. This chilling step allows the flavors to meld beautifully.
When ready to serve, top the Oreo fluff with the reserved crushed Oreos for an extra crunch and a beautiful presentation. Dive in and enjoy this delectable dessert!