Definitely an egg, as the DNA variations that led to the hen, actually revealed themselves firstly in the egg from non-100-percent-hen and non-100-percent-rooster parents,and then in the first 100-percent-hen; this process happened several times until finally a couple of 100-percent-hen and 100-percent-rooster met thus establishing the new species or variation (this taking out many details of course). After Darwin's studies and Watson and Crick discoveries, we still look at this as a kind of paradox just to (wisely) mantain cultural heritage from previous times.

If there is a God, he created the chicken who then laid the egg.

This question suffers from a logical fallacy known as a false dichotomy. In a false dichotomy (also called a false dilemma, either or, black or white, the missing middle) you are presented with two choices, when in fact there are more than two choices. If one choice is discredited, then the reader is forced to accept the other choice. Examples: "If today is not Tuesday, it must be Wednesday." "Evolution science is in disarray, so 'creation science' must be right." http://info-pollution.com/false.htm

chicken

you've gotta be kidding...