Prep the chicken: Slice chicken into thin, bite-sized strips. Pat dry. Season lightly with salt and pepper.

Make the sauce: In a small bowl, whisk soy sauce, oyster sauce, rice vinegar, brown sugar, sesame oil, red pepper flakes (if using), and chicken broth. In another small dish, stir cornstarch with 1 tablespoon water. Set both aside.

Chop vegetables: Keep pieces uniform so they cook evenly. Arrange them by cook time: onions and carrots first, then broccoli and peppers, then snap peas.

Heat the pan: Use a large skillet or wok. Add 1 tablespoon oil and heat over medium-high until shimmering.

Sear the chicken: Add half the chicken in a single layer. Cook 2–3 minutes per side until just cooked through and lightly browned. Remove to a plate. Repeat with the remaining chicken, adding a splash of oil if needed.

Cook the aromatics: Reduce heat slightly. Add another teaspoon of oil, then garlic and ginger. Stir 20–30 seconds until fragrant—don’t let them burn.

Stir-fry the veggies: Add onions and carrots. Cook 2 minutes, stirring often. Add broccoli and bell pepper. Cook 2–3 minutes until bright and just tender. Add snap peas for the final 1–2 minutes.

Combine chicken and sauce: Return chicken and any juices to the pan. Stir sauce base, then pour it in. Bring to a simmer.

Thicken the sauce: Stir the cornstarch slurry, then drizzle it into the pan. Toss everything until the sauce turns glossy and coats the chicken and veggies, about 1–2 minutes. If too thick, add a splash of water. If too thin, simmer another minute.

Taste and finish: Adjust salt, add more soy for savory depth, or a pinch more sugar for balance. Remove from heat. Top with green onions and sesame seeds.

Serve: Spoon over warm rice or noodles and enjoy right away.