Bake brownies according to package directions, allow to cool completely.
With an electric mixer blend together cream cheese and butter.
Add powdered sugar a little at a time, beating between additions until well incorporated
Add in vanilla and peppermint extracts and continue beating.
Add in green food coloring a few drops at a time until desired color is achieved (I used about 8 drops)
Spread frosting in a thick layer on cooled brownies.
Sprinkle mini chocolate chips across the top.
Cut into 24 square pieces & serve.