Slow cooker teriyaki chicken

Chicken second courses Japanese cuisine

2 lbs boneless, skinless chicken breasts 2 cloves garlic, minced ½ cup chopped white onion ½ cup honey ½ cup soy sauce (use low-sodium if desired) ¼ cup rice wine vinegar 1 Tbsp. chopped fresh ginger ⅛ tsp. freshly ground black pepper ¼ cup cold water 3 Tbsp. cornstarch (optional toppings: sliced scallions and toasted sesame seeds)