Set the cool whip and cream cheese on the counter to soften.
Add the Oreo cookies to a food processor and grind until semi fine pieces. If you do not have a food processor you can put the cookies into a gallon size freezer bag and zip it closed, then using a rolling pin crush the Oreos into small pieces.
Add the 6 tablespoons of butter to a microwave safe bowl and heat for 30-45 seconds until the butter is melted.
Dump the crushed Oreo cookies into a bowl, add the melted butter and use a fork to incorporate the butter into the cookie crumbs.
Spray a 9x13 pan with nonstick cooking spray. Using a spatula press the crumbs into the bottom of the pan.
Place the baking dish into the refrigerator while you work on the additional layers.
In a medium sized bowl use a hand mixer and mix the cream cheese with a mixer until light and fluffy.
Once fluffy add in 2 Tablespoons of milk, and sugar, and mix well. Stir in 1 and 1/4 cups Cool Whip.
Remove the crust from refrigerator and spread the mixture on top. Place back into the refrigerator.
In another bowl combine instant pudding with 3 and 1/4 cups cold milk. Whisk for several minutes until the pudding starts to thicken. Use a spatula to spread the mixture over the cream cheese layer and place back in the fridge for 5 minutes.
Spread the remaining Cool Whip over the top.
Sprinkle mini chocolate chips evenly over the top.
Place in the freezer for 1 hour, or the refrigerator for 3-4 hours before serving.