Now all we need to do is add our frosting. Take a plastic bag and add a big scoop of frosting or use a piping bag. You can use whatever frosting you like for this. Cream cheese frosting works out really well, or just use the store bought kind. Twist the bag, then snip off the corner with scissors. Next pipe the frosting onto one of the cookies, then place another cookie on top. Do this with all of them, and you are done!