Cut the raw chicken into bite-sized chunks and place in a medium sized mixing bowl. Add 1/4 cup of the oil, the cumin, paprika, oregano, garlic powder and salt, if used. Add the lime juice and thoroughly mix the ingredients to coat the chicken. Let rest for at least 10 minutes. 

Heat a wok, stir-fry pan or cast iron skillet over high heat and add the chicken mixture. Reduce heat to medium and stir-fry for 5-7 minutes or until chicken is cooked through. Remove from the pan and set aside. Add the onions, bell pepper and mushrooms to the pan and stir-fry until the onions are translucent and the vegetables are tender, about 6-8 minutes. Return the cooked chicken and the cilantro to the pan, stir to combine all ingredients and serve or garnish with more cilantro, if desired.