1) Season the chicken with black pepper than add to your slow cooker in a single layer. Whisk together the soy sauce, honey, tomato paste, rice wine vinegar, garlic, ginger, water, sesame oil, onion powder, and the chili sauce in a small bowl. 2)Pour the mixture over the chicken in the slow cooker. Set to low and cook until the chicken is cooked through and very tender (in my slow cooker it only needs 2 hours). 3)Transfer the chicken to a cutting board. Whisk the cornstarch with the remaining 1/4 cup water until combined, then add to the sauce in the slow cooker. Cover, set your slow cooker on high, and cook for about 20 minutes, or until the sauce has thickened slightly. 4)Meanwhile, shred the chicken into bite-size pieces. 5)Add the chicken back to the slow cooker and toss to coat with the thickened sauce. Serve garnished with the sesame seeds and scallions, if desired.