Some time ago, I applied to consulting firms and got offers from BCG, McK and OW. Since then, I have joined BCG and have continuing coaching candidates who have gotten offers at MBB. Being at BCG for 4 years, I know the interviewing process very well.
I like to understand the candidate's goals first, so as to best prepare the session.
My usual approach is to do a mock interview (15 minutes fit, 25-30 minutes case, 10-15 minutes of debrief) and have some time at the end to answer the candidate's questions.
All my cases include quant and qual, but I am happy to customize the case to best fit the candidate's needs.
The fit interview is based on real questions asked during MBB interviews.