I did this the other day. It's a portrait of a teenage Audrey Hepburn!
Photoshop, about an hour and a half. It would (should) have taken less time, but I got the proportions wrong from the start and then I spent most of the time correcting them, as you can see from the progress steps here:
Also, sketches from the previous two weeks:
First bunch is from transit, as usual. The second is from my new A5 sketchbook. It's got a very nice grain! I did some more photo studies and a couple poses from ImagineFX: Anatomy.