You could marinate the chicken in the refrigerator and keep it overnight.
With 12 medium sized green chilies, the spice level of the chicken was low-medium, you could increase green chilies if you want it to be spicy.
While shallow frying the chicken, make sure to fry all the sides of the chicken by turning it occasionally.
While cooking the chicken in the gravy, make sure to turn the chicken to different sides and cook after closing the dutch oven or pot with its lid.
You could run a fork into the chicken breast to check whether it has turned tender.
While serving, make sure to pour the gravy over the carved chicken, gravy enhances the taste of the chicken greatly.
After cooking the chicken, if you feel that the spice level is low, you could add ground pepper to make it spicy.