In food processor or blender process cookies until finely ground. Add butter and mix together completely. Press crumb mixture into bottom of greased 8 x 8 baking pan and bake 10 minutes. Cool to room temperature.
Melt chocolate in double boiler over slightly simmering water. Or microwave the chocolate, stirring every 30 seconds until completely melted. Pour half of the melted chocolate into pan and smooth evenly over crust. Place pan in refrigerator. Keep remaining chocolate warm.
To prepare the peanut butter filling, blend peanut butter and butter together until smooth, using a food processor or electric mixer. Slowly beat in icing sugar and then add vanilla. Beat until smooth. Spread peanut butter filling over the chilled chocolate layer. Finish by pouring remaining warm chocolate over filling and spreading smooth. Chill in refrigerator one hour or until firm. Cut into bars and serve.