Grease a 9x13 glass baking dish with butter and set aside.
In the bowl of a food processor, pulverize 2/3 of the Oreo cookies, reserving about 13 cookies to crush for the top of the dessert.
Add the melted butter to the cookie crumbs and pulse a few times to combine the crumbs with the butter.
Press the cookie crumb crust into the bottom of the prepared baking dish and place in the freezer to chill while preparing the next layer.
In a medium mixing bowl, beat cream cheese until smooth and fluffy.
Add 1/2 of the tub of Cool Whip and the powdered sugar (for extra sweetness) and beat a minute longer until the mixture is smooth.
Spread cream cheese mixture over the cookie crust, working carefully so that you do not lift the cookie crumbs and mix them into the layer.
Place the baking dish back into the freezer while preparing the pudding layer.
In a medium mixing bowl (you can use the same bowl and beaters you used to mix the cream cheese - no washing necessary!), beat together chocolate pudding mix and whole milk until pudding begins to thicken.
Spread pudding over the cream cheese layer in the baking dish.
Top the pudding layer with the remaining Cool Whip.
Crush the remaining Oreo cookies (I simply crushed them with a little mallet in a mixing bowl) and sprinkle them over the top of the prepared dessert.
Chill in the refrigerator for at least 4 hours (or the freezer for 2 hours) before slicing into squares and serving.
Notes
Store, covered, in the refrigerator for 3-4 days. Freeze for up to 3 months. Defrost in the refrigerator before serving.You can crush the Oreos in a ziploc bag with a rolling pin if a food processors isn’t available. Then, dump the crumbs directly into the baking dish and mix with the melted butter right in the dish.No need to wash the bowl and beaters between mixing up the layers. The remnants from the cream cheese layer will just beat and blend right into the pudding layer.You can use already prepared chocolate pudding for an even quicker dessert!The Cool Whip adds some sweetness to the cream cheese layer, but we liked just a tad more - powdered sugar sweetens up the cream cheese easily!