Season sliced chicken with salt & pepper. Toss with 1 tbsp cornstarch.
Whisk soy sauce, water, honey, rice vinegar, sesame oil, garlic, ginger, and cornstarch. Set aside.
Add cashews to a dry pan and toast 2–3 minutes until golden (optional). Remove.
Heat oil in a pan over medium-high (375°F / 190°C). Add chicken and stir-fry 5–6 minutes until golden. Remove to a plate.
Add bell pepper, broccoli, carrot, and white onion. Cook 3–4 minutes until crisp-tender.
Return chicken. Pour in the teriyaki sauce. Stir 1–2 minutes until the sauce thickens and becomes glossy.
Add green onions + toasted cashews (if using). Toss and remove from heat.
