Wow. Any of these would be good, but all will be too much. First chop or thinly slice the chicken. I usually reconstitute the couscous in chicken broth (which usually negates the need for the salt). Because you have an embarassment of riches here, I'd recommend using whatever is most likely to go bad; in my house it would be the courgette and/or the mushrooms. We love both, but they don't have as long a shelf life as some other vegs). Onions go into everything, period. If you have a curry powder you like, then the other herbs will be superfluous and the curry powder probably contains coriander. You won't taste them above the curry powder. Anyway, stir fry (sautee, pretty much the same thing) the chicken, onions, and mushrooms/courgette (for those who know it by another name, zuchini) with the spices (choose the curry powder or the others) in a little oil. Then toss in water or broth, and couscous. Lower flame (or in my case, an electric burner, I just turn it off) and cover until the couscous is rehydrated.
If your chick peas are canned, they can go in any time or be saved for another meal.
I don't see where you're from. If the coriander is the fresh leaves (as opposed to the dried seeds), then you put them in right before serving. A rough chop. Ditto the lemon or lime, a touch of juice and maybe a julienne of some skin. These all give a fresh, bright flavor that is best put in at the end (OK, just my opinion).
If you happen to have some dried fruit (raisins, dates, etc) and nuts (pistachios, almonds or pine nuts in particular) toss in a hand full.
Just before serving, take two forks and toss and fluff. Taste to see if it needs salt, pepper or heat to your taste.
This is probably one of my husband's favorite dishes.
