Preheat the oven to 375°F (190°C) and lightly oil or spray a baking dish.
Whisk together the sauce: soy sauce, chicken stock, hoisin sauce, rice vinegar, sesame oil, brown sugar or honey, grated ginger, minced garlic, cornstarch, crushed red pepper, cracked black pepper, and sriracha if using.
Place the chicken pieces, broccoli florets, diced red peppers, chopped green onions, and cashews in a large mixing bowl or directly in the prepared baking dish.
Pour the sauce over the chicken and vegetables and toss until everything is evenly coated. Season with salt to taste (and additional pepper or garlic powder if desired).
Arrange the mixture in a single layer in the baking dish if not already there.
Bake for 20–24 minutes, or until the chicken reaches an internal temperature of 165°F (74°C) and vegetables are tender-crisp.
Remove from the oven and let rest for a few minutes so the sauce thickens slightly. Serve over rice or as desired and sprinkle with sesame seeds if desired.