Separate Oreo and discard (or eat) filling. Place cookie halves in a small plastic bag and crush into a fine crumb with a rolling pin or the bottom of a heavy glass. Set crumbs aside.
In a medium bowl combine softened butter and cream cheese. Beat until smooth.
Add powdered sugar, cookie crumbs, salt, and 1 teaspoon of milk or cream. Beat until sugar is completely incorporated and frosting is fluffy. Add up to 2 teaspoons more of milk or cream if necessary until frosting reaches your desired consistency.
Frost something delicious and enjoy!
Notes
* A large open star tip is my favorite for piping frosting.* If using salted butter, omit the pinch of salt. This recipe yields 3/4 to 1 cup of frosting and will dramatically frost four to five cupcakes with big swirls or frost about eight cupcakes or cookies with a knife.