Combine powder sugar and cocoa together in a medium sized bowl. Set aside.
Beat butter and vanilla together in a mixing bowl for at least 2 minutes.
Add the dry mixture to your butter. Mix.
Slowly add milk a tablespoon at a time, beating constantly, till you reach the desired consistency.
Frost your cake or cupcake.
Enjoy!
Recipe by Emily Reviews at https://www.emilyreviews.com/2019/04/making-the-most-of-our-butler-pantry-with-john-boos-chocolate-buttercream-frosting-recipe-giveaway.html