Add chicken and sliced onion slices and garlic salt. Cover with lid and turn heat to down to medium and simmer for 12-14 minutes.
Cut mushrooms in halves. (brush off excess dirt with dry paper towel)Cut avocado into spears. Wash cilantro and cut into small chopped pieces. (including stems)
While chicken is simmering, at 7-9 minutes, add mushroom halves, cilantro, salt, cumin and replace lid for the remainder of time.
Remove from heat immediately. (preventing overcooking)