In a large bowl, combine onion, garlic, honey, soy sauce, hoisin, vegetable oil and red pepper.
Place chicken breasts into slow cooker, and pour sauce mixture over chicken. Cover and cook on low heat for 3 hours and 30 minutes.
In a small bowl, add cornstarch and ¼ cup of sauce from slow cooker. Mix with whisk until dissolved, and pour back into slow cooker. Gently stir the sauce. Cover and cook for approximately 15-20 minutes.
Garnish with sliced green onions and sesame seeds.
