Prep the chicken: Pat the chicken dry and season lightly with salt and pepper. Toss with the cornstarch until evenly coated.
This helps the chicken brown and thickens the sauce later.
Mix the sauce: In a small bowl, stir together the sweet chili sauce, soy sauce, and rice vinegar. Set it near the stove. If you like heat, add a pinch of red pepper flakes.
Heat the pan: Place a large skillet over medium-high heat and add the oil.
When it’s shimmering, it’s ready.
Sear the chicken: Add the chicken in a single layer. Don’t crowd the pan. Cook 3–4 minutes without moving, then flip and cook 2–3 minutes more until mostly cooked through and golden.
Add aromatics: Add the white parts of the green onions, garlic, and ginger.
Cook 30–45 seconds, stirring, until fragrant. Keep it moving so the garlic doesn’t burn.
Veg time: Add bell pepper and snap peas. Stir-fry 2–3 minutes until the veggies are crisp-tender and bright.
Sauce it up: Pour in the sauce mixture.
Toss everything to coat. Let it bubble for 1–2 minutes until glossy and slightly thickened. Stir in sesame oil if using.
Finish and serve: Turn off the heat.
Top with green onion tops and sesame seeds. Taste and adjust with a pinch of salt, extra vinegar, or more chili sauce as needed. Serve over rice or noodles.