In a medium bowl, combine the crushed chocolate sandwich cookies and melted butter. Press the mixture into the bottom of a 9×13 inch baking dish. Refrigerate while preparing the filling.
In a large bowl, beat the softened cream cheese, granulated sugar, 2 tablespoons milk, and vanilla extract until smooth and creamy. Fold in 4 ounces (about one-third) of the whipped topping. Spread this mixture evenly over the cookie crust.
In another large bowl, whisk together the instant chocolate pudding mix and 2 1/2 cups cold milk for 2 minutes, or until thickened. Spread the pudding mixture over the cream cheese layer.
Top with the remaining 8 ounces of whipped topping.
If desired, sprinkle with mini chocolate chips.
Refrigerate for at least 4 hours, or preferably overnight, before serving.
Notes
For best results, use full-fat cream cheese.
Ensure the cream cheese is at room temperature to prevent lumps.
This dessert can be made a day in advance.
Store leftovers in the refrigerator for up to 3-4 days.