Put the chicken in a heated frying pan and caramelize the meat. After a few minutes add the onion and chili (if you like you can also add some finely sliced bell pepper). After a few minutes add the seasoning mix and stir well. Leave on a low heat for a couple of minutes more, so the flavors can mix in the dish.
Serve the fajitas with all the sidedishes, so everybody can assemble his own personal mexican taste bomba