In a medium bowl place all the ingredients except cornstarch, 1/4 cup water, sesame seeds and lettuce combine well and pour over chicken. Cook on low 4 hours. Remove chicken from slow cooker and shred with forks.
Combine the cornstarch and 1/4 cup water. Pour into sauce in slow cooker. Cook until thickened about 20 minutes. Add the chicken back to slow cooker and cook another 20 minutes.
Serve on lettuce leaves and garnish with sesame seeds if desired