Prep the chicken and beans: Pat the chicken dry and season lightly with salt and pepper. Trim the ends off the green beans and cut them in half.
Mince the garlic and ginger.
Make the sauce: In a small bowl, whisk the soy sauce, honey, rice vinegar, and chicken broth. In a separate cup, stir the cornstarch with 2 tablespoons of water to make a slurry. Set both aside.
Sear the chicken: Heat 1 tablespoon of oil in a large skillet over medium-high heat.
Add chicken in a single layer. Cook 4–6 minutes, stirring once or twice, until browned and just cooked through. Transfer to a plate.
Sauté the green beans: Add the remaining 1 tablespoon of oil to the skillet.
Toss in green beans and a pinch of salt. Cook 4–5 minutes, stirring occasionally, until bright green and crisp-tender.
Add aromatics: Push beans to the side. Add garlic and ginger to the open spot.
Cook 30 seconds, stirring, until fragrant, then mix with the beans.
Combine and simmer: Return chicken to the pan. Pour in the soy-honey mixture and red pepper flakes if using. Bring to a gentle simmer, about 1 minute.
Thicken the sauce: Stir the cornstarch slurry, then pour it in while stirring.
Simmer 1–2 minutes until the sauce turns glossy and clings to the chicken and beans. If too thick, splash in a bit more broth or water.
Taste and adjust: Add more vinegar for brightness or honey for sweetness. Season with black pepper.
Salt lightly only if needed, since soy sauce is salty.
Serve: Garnish with sesame seeds and sliced green onions. Spoon over rice or noodles, or keep it simple and serve as-is.