Prepare the sauce by whisking together hoisin sauce, soy sauce, rice vinegar, honey, sesame oil, water, and cornstarch (if using). Set aside.
Heat oil in a large wok or skillet over high heat.
Add sliced pork and stir-fry for 3–4 minutes until lightly browned and cooked through. Remove from the pan and set aside.
Add the onion, garlic, and ginger to the pan and cook 1 minute until fragrant.
Add broccoli, bell pepper, carrots, and snow peas. Stir-fry for 4–5 minutes until vegetables are crisp-tender.
Return the pork to the pan.
Pour the hoisin sauce mixture over the pork and vegetables. Cook 1–2 minutes, allowing the sauce to thicken and coat everything evenly.
Taste and adjust seasoning if needed.
Serve hot with rice, noodles, or lettuce wraps.