1) In a (measuring) jug, add the BBQ sauce, Worcester sauce, and brown sugar. Grate the onion, if you’re using it, into the sauce mixture and mix together.
2) Place the chicken in the bottom of the slow cooker pot. Pour the sauce over the chicken and make sure that each breast is covered.
3) Cook on low for six to seven hours or on high for three to four hours.
4) When cooked, take the chicken out and place onto a chopping board or other clean, flat surface. Using two forks, tear the chicken (this should be very easy as the chicken should be tender if cooked) into small pieces and then add to the slow cooker pot and mix in with the sauce.
5) Serve it up. It goes perfectly in sandwiches or on pasta. You can also place it into a covered pot and leave it in the fridge for up to two days.