Place the chicken and chopped garlic in the bowl of a slow cooker.
In a mixing bowl, whisk together tamari (or soy sauce), ketchup, honey, chili paste, rice vinegar, and black pepper until combined.
Pour the sauce over the chicken in the slow cooker, then add the broccoli florets on top or around the chicken.
Cover and cook on low for 3–4 hours (or on high for 1–2 hours) until the chicken is cooked through and tender.
Increase the slow cooker to high and remove the lid; cook uncovered about 25 minutes to reduce and thicken the sauce.
Serve the chicken and broccoli over rice and top with chopped scallions/cilantro and toasted sesame seeds.
