This frosting is a lighter version of cookies and cream since it's made with meringue. It is the same Italian meringue recipe found here, but with the exception that when it's done, a cup of crushed Oreos is folded in. Because of the grease found in the Oreo's filling, when it comes into contact with the meringue, its consistency will be a little on the flat side like a marshmallow cream. You can still decorate well with it, and when pipped on the cupcake it will hold its shape. One option to improve the consistency of the meringue is to remove the white cream and just add the crushed cookies, this way you will have less fat incorporated into the meringue. Another option is to use vanilla buttercream or white chocolate buttercream mixed with the crushed Oreos.
At the bottom of each half cupcake liner place half of a cookie, if you prefer, you can use a whole cookie, but this will decrease batter size.