Using a stand mixer, cream together the cream cheese and butter on medium-high until creamy, light, and fluffy (about 7 minutes).
Mix together the cornstarch and chocolate extract (it'll be thick!), then add to the cream cheese mixture.
Mix for two minutes on medium-high, then (on low) gradually add the powdered sugar and cocoa powder. Once incorporated, mix on medium-high again until super fluffy, about 5-7 minutes.
Refrigerate at least 30 minutes, or overnight.