1)Line 23cm square slab pan with foil. Blend or process biscuits until fine, stir in butter. Press crumb mixture evenly over base of prepared pan, refrigerate while preparing caramel filling. 2)Spread filling evenly over base, refrigerate until firm. Spread evenly with topping, refrigerate until firm. CARAMEL FILLING)Combine caramels, butter and milk in pan, stir over low heat until caramels are melted(a few white pieces will not dissolve). TOPPING)Combine chocolate and butter in small bowl.