The sauce that may have been on chimichangas that you have could be a basic verde sauce. It is made from mild green diced chili peppers and you can put it on chicken enchiladas, on chimichangas, on chicken burritos. It is what we used at chi-chi’s. I don’t remember what was in theirs, but I have made a replica using mexican websites. Just look for a recipe for a verde sauce. I have mexican employees and they love it.