Mix crushed cookies and butter in a foil-lined 9 inch square pan. Press firmly onto bottom of pan to form a crust.
Beat cream cheese in a large bowl with electric mixer on low speed until creamy. Gradually add condensed milk, mixing well after each addition. Blend in chocolate (which has been melted according to package directions), then gently stir in whipped topping. Spoon mixture over crust, then sprinkle with extra Oreo cookie crumbles.
Cover tightly with plastic wrap, then freeze at least 6 hours or overnight. Remove from freezer about 15-20 minutes before serving to soften slightly. Cut into squares to serve. Keep leftover dessert in the freezer. ENJOY!!!