Wash and pat dry chicken breasts, then rub with jerk paste and add chopped onions.
Let marinate for at least 1 hour in the fridge.
In a bowl, mix BBQ sauce, Worcestershire sauce, brown sugar, and jerk paste.
Add chicken to slow cooker and pour sauce over; stir to coat.
Cover and cook on high for 3½ hours or until chicken is tender.
Remove chicken and shred with two forks.
Return shredded chicken to cooker and let soak in sauce for 10 minutes.
Layer rolls with pulled jerk chicken and top with pineapple chutney.