1) There's the well-known Secretary (or Marriage, or Sultan's Dowry) Problem (http://en.wikipedia.org/wiki/Secretary_problem). It has three caveats, though:
* Solution assumes that you have a lot of (e.g. ~20) candidates.
* It is assumed that you can sum up each candidate's ability in a single number. This is the hardest part, since the human mind works relationally and assigning absolute numbers to anything is hard.
* The probability of picking the best candidate is only 1/e.
But at least there's a guaranteed bound on the probability of success, that some of the other methods lack.
2) (If possible) Hire the engineer and HR person at the same time and have the HR candidates evaluate the engineering candidates. Then run Knuth's stable marriage algorithm (http://en.wikipedia.org/wiki/Stable_marriage_problem) to pick the best candidates for each.