Who is Tina Tchen, the attorney linked to Jussie Smollett messages?

"Tina Tchen, the attorney and former chief of staff to first lady Michelle Obama, has garnered scrutiny after messages traded with Cook County State's Attorney Kim Foxx – about the alleged hoax linked to actor Jussie Smollett – emerged shortly before prosecutors dropped all charges against Smollett on Tuesday."

https://www.foxnews.com/us/who-is-tina-tchen-the-attorney-linked-jussie-smollett-messages