Coarsely chop 15 cookies. Finely crush remaining cookies. Mix with butter. Press on to bottom of 13x9 inch pan. Refrigerate while preparing filling. Beat cream cheese,sugar,and vanilla in large bowl with mixer until well blemded. Gently stir in 2 1/2 cups cool whip and chopped cookies. Spoon over crust.
Refrigerate 4 hours or until form. Serve with remaining cool whip.