Start by cutting the chicken breasts into 1-inch pieces. Trim the ends of the green beans and mince the garlic and ginger. Having everything prepped and ready to go will make the cooking process much smoother.
In a wok or large skillet, heat 1 tablespoon of vegetable oil over medium-high heat. Allow the oil to get hot but not smoking.
Add the chicken pieces to the pan in a single layer. Cook for about 5-7 minutes, stirring occasionally, until the chicken is browned and cooked through. The internal temperature should reach 165°F (75°C). Remove the chicken from the pan and set aside.
In the same pan, add the trimmed green beans. Stir-fry them for about 3-4 minutes until they are bright green and tender-crisp. You might need to add a splash of water to help steam them a bit.
Once the green beans are cooked, add the minced garlic and ginger to the pan. Stir-fry for about 1 minute until fragrant, being careful not to burn them.
Return the cooked chicken to the pan with the green beans. In a small bowl, mix together the soy sauce, oyster sauce, rice vinegar, sugar, and cornstarch mixture. Pour the sauce over the chicken and green beans, stirring until everything is evenly coated and the sauce thickens slightly, about 2-3 minutes.
Once everything is heated through and well combined, remove the stir-fry from heat. Serve it immediately over steamed rice or noodles for a complete meal!
