Grill the marinated chicken breast and slice or shred your store bought rotisserie chicken. Set aside.
Heat a pan or skillet over medium-high heat. Add some olive oil and sauté the chopped onions and mushrooms for a few minutes. Add the lime juice, chili powder, ground cumin, black pepper and red pepper (if adding) and mix well. If using rotisserie chicken, add the shredded chicken to the pan and mix well.
In a separate bowl, combine the black beans and salsa. Cook or heat your tortillas.
To assemble: Sprinkle the shredded cheese on the warm tortillas, please some chicken breast down the center of each tortilla, top with the onions and mushrooms. Add the tomatoes, spoon on the bean/salsa mixture and add the green onions on top.