Step 1: In a medium bowl, combine the finely crushed Oreo cookies and melted butter. Press this mixture firmly into the bottom of a 9x13 inch baking dish. Place in the freezer for 10 minutes to set while you prepare the next layer.
Step 2: In a large bowl, beat the softened cream cheese and powdered sugar with an electric mixer until smooth and creamy. Gradually beat in 1/2 cup cold milk until well combined.
Step 3: Gently fold in half of the whipped topping (about 4 oz) into the cream cheese mixture until just combined. Spread this creamy layer evenly over the chilled Oreo crust.
Step 4: In another large bowl, whisk together the instant chocolate pudding mix and 3 cups cold milk for 2-3 minutes, until the pudding starts to thicken. Pour and spread the pudding layer gently over the cream cheese layer.
Step 5: Carefully spread the remaining half of the whipped topping over the pudding layer. Smooth it out with a spatula.
Step 6: Decorate the top with festive sprinkles, crushed Oreos, or other holiday garnishes if desired.
Step 7: Cover the dish loosely with plastic wrap and refrigerate for at least 3-4 hours, or preferably overnight, to allow all layers to set completely. Slice and serve cold.