Trim fat from pork. Place pork or chicken in a plastic bag set into a shallow dish.
For marinade, combine chicken broth, lime juice, olive oil, brown sugar, garlic, mint (if you like), and dried pepper flakes. Pour over the pork or chicken. Seal bag.
Marinate in the refrigerator for at least 6 hours or up to 24 hours. Turn the bag occasionally.
Remove pork or chicken from the bag, reserving marinade.
Grill pork or chicken on the rack of an uncovered grill directly over medium* coals until juices run clear for pork or chicken is no longer pink, turning once halfway through grilling time and brushing with marinade up to the last 5 minutes of grilling time. (Allow 8 to 10 minutes for pork chops and tenderloin or 12 to 15 minutes for chicken.) Makes 4 servings.
To test for medium heat, you should be able to hold your hand over the heat at food height for 4 seconds for medium before having to pull away.