Melt the butter in an 8" skillet or fry pan, add chicken, salt, pepper and some chili powder. When chicken is browned on both sides remove it to a plate. Put the cream of mushroom soup in the skillet, add teriyaki sauce and milk mixing until soup is smooth. Add more salt, pepper and chili powder to taste. Add mushrooms if desired, fresh or canned. Put cooked chicken pieces back into skillet until thoroughly warmed and covered in sauce. You may need little more milk if you have a lot of chicken. There is normally enough sauce to cover the chicken and some for the rice, noodles or mashed potatoes served with it. The sauce should have a mellow taste not to cover up the chicken but normally has a spicy, warm aftershock.