Sandy is your man:

he helped me walk into the interview with confidence and very well prepared. He provided perspective on how the interview would go, the kind of questions asked, and what is being assessed. Sandy fired many questions at me, some of which I had prepared and some of which I hadn’t prepared, making it a proper mock interview. Sandy would then jump in and provide guidance and tips on how to improve so by the time I walked into the real interview I felt confident about what I had to say. If you want to get a taste of what the HBS interview will be like, I highly recommend doing a mock one with Sandy.