Chow Mein is basically fried noodles. You can fry these noodles with anything-leftover meat such as chicken or beef and adding some broccoli or cauliflower. I even tried canned fish chow mein, and it was not bad.
I usually add Chinese spicy sauce. I think the sauce is a little sour. If I fry with meat I add BBQ sauce to balance the spicy sauce. BBQ sauce is tangy and savory, it surprisingly goes well!
Good Luck with your Chow Mein!!