Add the sliced onions and chopped bell peppers to the bottom of the slow cooker. Season the chicken with the salt and half of the pepper, garlic powder, onion powder and all of the paprika and place the chicken on top of the vegetables.
In a small bowl, whisk together the chicken broth, soy sauce, dry sugar, Worcestershire sauce, minced garlic, ginger paste and the rest of the black pepper, onion powder and garlic powder. Pour it over the chicken and vegetables.
Cover and cook on LOW for 5 to 6 hours or HIGH for 2½ to 3½ hours, until the chicken is tender and fully cooked. Remove the chicken from the slow cooker and shred it with two forks or cut it into bite sized pieces. Return it to the slow cooker.
In a small bowl, whisk together the cornstarch and cold water until smooth. Stir it into the slow cooker. Cover and cook for another 15 to 20 minutes, or until the sauce has thickened. Serve over steamed rice or noodles and garnish with sliced green onions and sesame seeds, if desired.