Combine soy sauce, oyster sauce, hoisin, rice vinegar, sesame oil, honey, garlic, ginger, white pepper, and red pepper flakes in a small bowl or jar. Stir or shake until fully combined.
In a separate small bowl, whisk cornstarch and water together until completely smooth with no lumps. Keep separate from the sauce until ready to use — cornstarch settles if it sits too long.
Taste the sauce before cooking. It should be savory, slightly salty, a little sweet, and well-seasoned. Adjust — more rice vinegar if too salty, more soy if too sweet, more honey if too sharp.
Cook vegetables and protein in a very hot wok or skillet until done. Push everything to the sides. Stir the cornstarch slurry into the sauce, then pour the combined sauce into the center of the pan. Stir continuously for 30–60 seconds until glossy and thickened. Toss everything together to coat evenly.
Serve over steamed rice or toss through cooked noodles. Top with sliced spring onions and toasted sesame seeds.
