Preheat oven to 350F degrees. Spray a 9 x 13-inch baking pan with nonstick cooking spray.
In a bowl, combine cake with with water, oil, eggs and 1 cup of peanut butter. Stir until combined well.
Pour batter into prepared baking dish and bake for about 23-28 minutes.
A toothpick inserted into the middle of the cake should come out clean when cake is done. Allow cake to cool completely before frosting.
Then in a medium bowl, combine chocolate frosting with leftover (¼ cup) peanut butter. Stir until combined.
Spread frosting onto cooled cake.
Place 4 or 5 cookies (more if you like lots of cookies) into a ziploc bag. And crush the cookies using a heavy object like a rolling pin. Sprinkle crushed cookies onto cake.