Wash the green beans, trim the ends, and cut them into 2-inch pieces. Slice the onion into thin strips. For the chicken, cut it into thin, bite-sized strips. A sharp knife will really help to speed up this step!
Grab a small mixing bowl and whisk together the soy sauce, oyster sauce, rice vinegar, sesame oil, sugar, chicken broth, and cornstarch. Stir well until smooth. This is where the magic happens!
Heat a tablespoon of cooking oil in your wok or skillet over medium-high heat. Once it’s hot, add the chicken strips. Stir-fry for 3–4 minutes until cooked through and golden brown. Remove the chicken from the pan and set aside.
Using the same pan, add another touch of oil and toss in the green beans and onions. Cook for 3 minutes until the veggies are slightly tender but still crisp. For extra flavor, toss in minced garlic or grated ginger if you like.
Return the chicken to the pan. Pour the sauce over the chicken and veggies. Stir everything together so it’s coated evenly. Cook for another 2 minutes until the sauce thickens slightly.