Rub the chicken breasts with olive oil and place them in the bottom of a slow cooker.
Whisk together the soy sauce, honey, blackberry preserves, sweet chili sauce, hoisin sauce, rice wine vinegar, garlic, ginger, salt, and pepper.
Pour HALF of the sauce over the chicken. Refrigerate the other half until later. Cook on LOW for 5-6 hours or on HIGH for 3-4 hours or until chicken is tender enough to shred.
Remove the chicken from the slow cooker and shred it. Meanwhile, strain any excess liquid from the slow cooker into a small saucepan. Whisk the cornstarch and reserved sauce together in the saucepan with the juices.
Bring the liquid to a gentle boil then reduce heat and simmer until it has thickened, stirring occasionally.
Return the shredded chicken to the slow cooker and pour the sauce over the top, toss to coat, and enjoy!
Notes
*You can find hoisin sauce in the Asian section of your grocery store.