Prep the chicken and beans. Pat the chicken dry and season lightly with salt and pepper. Trim the green beans. Stir together soy sauce, honey, rice vinegar, sesame oil, garlic, ginger, and red pepper flakes in a small bowl.
Blister the green beans. Heat 1 tablespoon oil in a large skillet over medium-high.
Add the beans with a pinch of salt. Cook 4–5 minutes, tossing occasionally, until bright green with some charred spots and crisp-tender. Transfer to a plate.
Sear the chicken. Add remaining 1 tablespoon oil to the skillet.
Add the chicken in an even layer. Cook 5–7 minutes, stirring once or twice, until browned and cooked through. Avoid crowding; work in batches if your pan is small.
Add the sauce. Pour the honey-garlic mixture into the skillet.
Stir to coat the chicken and bring to a simmer. If you like a glossy, thicker sauce, stir in the cornstarch slurry and cook 1–2 minutes until it slightly thickens.
Return the beans. Add the green beans back to the pan and toss everything together. Cook 1–2 minutes more so the flavors meld and the beans warm through.
Taste and finish. Adjust seasoning with a splash more soy for salt, honey for sweetness, or vinegar for brightness.
Sprinkle with sesame seeds and scallions if you like.
Serve. Spoon over warm rice or noodles, or serve straight from the skillet for a lighter meal.