Preheat oven to 350 degrees. Spray two 8-inch cake pans with cooking spray.
In a medium bowl whisk together the eggs, water, and vegetable oil. Add the cake mix and mix well until fully combined. Divide the batter equally among the prepared cake pans. Bake for 20-25 minutes or until risen and a toothpick inserted into the center comes out clean. Let cool in the pans for 110 minutes then remove to a cooling rack to fully cool.
In the bowl of an electric mixer fitted with the paddle attachment, beat the shortening until fluffy, about 1 minute. Add the powdered sugar, vanilla, and salt. Beat well. Add milk, 1 tablespoon at a time, until it reaches a spreadable consistency. Transfer a third of the mixture to a small bowl.
Crush 6 cookies well and add to the third frosting in the small bowl.
Cut the doomed parts off the top of the cakes to make flat. Place one layer on a cake stand. Spread the frosting with the cookies mixed in on the top. Top with the last layer and spread the frosting without the cookies around the sides and top. Decorate with extra frosting and cookies.