This was a tough lighting setup to get right. I still don't think I got it, but I'm closer now than when I started. The principle is pretty simple: use hard, directional lighting to make a portrait. Karsh's lighting is theatrical, it's motivated and has purpose.
I used the reflector off of a desk lamp to help direct the front light. The two flashes behind me were snooted with home-made gaffer tape snoots.
I have to say, this would have been a lot faster had I taken the photos while tethered, and using a remote trigger. The shallow depth of field is very tough to work with when you're running to and from the camera.