2) Add the onions and cook until translucent, about 2 minutes. Add the red peppers, garlic, salt and pepper, and allspice and cook for 2 minutes more.
3) Stir in the vinegar, molasses, Worcestershire sauce, lime juice and tomato sauce and cook for 1 minute more. Transfer the mixture into a bender and add the mango and jalapeno. Blend until smooth.
4) Put 240ml of the barbecue sauce into a sealable plastic bag with the chicken and marinate for 1 hour.
5) Preheat the broiler. Put the chicken on a broiler pan and discard the marinade. Broil the chicken on high for about 12 minutes, turning once. Let the meat rest for 10 minutes before slicing. Spoon about 120ml of barbecue sauce over the meat slices and serve.