Prepare the chicken
Season the chicken with salt and pepper. Sprinkle with the sesame seeds, coating evenly and patting firmly so they adhere to the chicken.
Cook the chicken and vegetables
In a wok or large frying pan over high heat, warm the peanut oil. Add the chicken and cook, stirring often, until golden and nearly opaque throughout, 3–4 minutes. Transfer the chicken to a plate. Add the bell pepper, sugar snap peas, and garlic and stir-fry until the vegetables are barely tender-crisp, 1–2 minutes.
Finish the dish
Return the chicken to the pan with the vegetables and add the broth, soy sauce, vinegar, and sesame oil. Reduce the heat to medium and simmer until the chicken is opaque throughout and the sauce is slightly reduced, about 2 minutes. Transfer to plates or shallow bowls, sprinkle with the cilantro, and serve.