Interesting. So it originally meant "to fry something in preparation" (i.e., ahead of time), and was then picked up by others who were unaware of its real semantics, thought it just a fashionable way of saying "to fry", adopted it to sound cool, and it is now a part of every would-be chef's vocabulary with a bastardised meaning (or no meaning at all, depending on one's point of view). Ah well.
Incidentally, I just did some web-based research myself on the phrase, and several of the discussions are delightful, but I think this one is surely la cr