Prep the chicken. Pat the chicken dry and cut into bite-size pieces. Toss with 1 tablespoon cornstarch and a pinch of salt and pepper.
This gives a light crisp and helps the sauce cling.
Make the sauce. In a small bowl, whisk soy sauce, rice vinegar, honey, ginger, garlic, sesame oil, red pepper flakes, water, and 1 teaspoon cornstarch until smooth. Set aside.
Cook the veggies. Heat a large nonstick skillet or wok over medium-high heat. Add 1/2 tablespoon oil.
Stir-fry broccoli, bell pepper, and snap peas for 3–4 minutes until crisp-tender. Sprinkle with a pinch of salt. Transfer to a plate.
Brown the chicken. Add the remaining 1/2 tablespoon oil to the hot pan.
Add chicken in a single layer. Cook 4–6 minutes, stirring occasionally, until golden and cooked through. Avoid overcrowding; work in batches if needed.
Combine and sauce. Return veggies to the pan.
Give the sauce a quick stir and pour it over. Toss for 1–2 minutes until glossy and slightly thickened. Stir in the white parts of the green onions.
Finish and serve. Remove from heat.
Sprinkle with toasted sesame seeds and the green onion tops. Serve over rice or cauliflower rice, with a squeeze of lime if you like.