Here's how I used it. Hope this helps!
Dear Dr. ______, I hope the new year is treating you well! In applying for the ________'s Clinical Psychology PhD program this fall 2021, I listed you as a strong mentor fit. I understand the interview selection is considerably underway, and certain faculty already finalized their candidate list. However, because others have not yet extended all invitations, I heard from the department that applications are still being reviewed. With this is mind I am wondering - have all interviews been extended from your side? I would really appreciate your update.
I look forward to hearing back. Have a great day!