In a small bowl, mix the soy sauce, cornstarch, water, and sesame oil. Set aside.
Heat 1 tablespoon of vegetable oil in a large skillet or wok over medium-high heat. Add the sliced chicken and season with salt and pepper. Cook for about 5-7 minutes, or until the chicken is browned and cooked through. Remove the chicken from the skillet and set aside.
In the same skillet, add the remaining tablespoon of vegetable oil. Add the minced garlic and ginger, stirring for about 30 seconds until fragrant.
Add the green beans to the skillet and stir-fry for about 3-4 minutes until they are bright green and tender-crisp.
Return the cooked chicken to the skillet and pour the soy sauce mixture over the chicken and green beans. Stir well to combine and cook for an additional 2-3 minutes, allowing the sauce to thicken slightly.
Serve the stir fry over cooked rice or noodles.