For OREO Ganache: Bring water to boil in small saucepan. Combine remaining ingredients in medium bowl. Add boiling water; let stand 3 to 4 min. Pour mixture into food processor or blender. Process 20 seconds. Pour back into bowl to cool. Let stand several hours or overnight.
For Pie: Combine OREO Base Cake and butter until well blended. Firmly press onto bottom and up the side of 9-inch inch pie plate. Fill with pudding. Top with cake layer, pressing to create an even top. Refrigerate until pudding is set.
Pour OREO Ganache over cake layer and spread evenly. Sprinkle cookie pieces around outer edge of pie.