Reserve ½ cup of the crushed Oreos for the topping. Mix the remaining crushed Oreos with the melted butter until evenly coated. Press firmly into an ungreased 9x13-inch baking dish. Freeze for 10 minutes.
Beat the softened cream cheese and powdered sugar with a hand mixer on medium speed for about 2 minutes, until smooth. Fold in half of the Cool Whip, about 6 ounces. Spread evenly over the chilled Oreo crust.
Whisk the instant chocolate pudding mix and cold milk together for about 2 minutes, until thickened. Spread carefully over the cream cheese layer.
Spread the remaining Cool Whip over the pudding. Sprinkle the reserved Oreo crumbs over the top.
Cover and refrigerate for at least 4 hours, or overnight, before slicing.