As of 2015, Betty Crocker offers a cookie brownie mix. This mix makes dessert bars that are a combination of a chocolate chip cookie and a brownie. Individuals who want cookie pieces in their brownies can mix 1 cup of crushed cookies into their brownie batter before baking.
Instead of using crushed cookies, try adding whole cookies to a pan of brownies. Prepare the brownie mix as directed, then pour half of the batter into the prepared pan. Place a layer of cookies, such as chocolate sandwich, chocolate chip or peanut butter cookies, over the brownie batter. Pour the remaining batter on top of the cookies, and bake as usual.