Preparation Combine oyster sauce, vinegar, soy sauce, brown sugar, and 1 Tbsp. water in a small bowl; set aside. Heat 2 Tbsp. oil in a large nonstick skillet over medium. Add cashews and tilt skillet toward you so that the oil pools around cashews. Toast cashews, tossing and spooning oil over constantly, until cashews are golden brown, about 3 minutes. Transfer cashews to a small plate and let cool, reserving oil in skillet. Cut chicken into 1/2"-thick slices. If any slices are longer than 2", cut in half crosswise. Season chicken with salt and coat with cornstarch, tossing chicken to evenly distribute cornstarch. Increase heat to medium-high and cook chicken in a single layer in same skillet, undisturbed, until golden brown underneath, about 3 minutes. Turn and cook until other side is just opaque, about 1 minute. Transfer chicken to a plate (it won’t be totally cooked through; don’t worry as it will finish cooking in the sauce). Cook beans and onion in same skillet, tossing often, until beginning to soften and brown in spots, about 4 minutes. Add remaining 1 Tbsp. oil followed by garlic and ginger. Cook, tossing often, until garlic and ginger are softened, about 1 minute longer. Add reserved sauce and return chicken to skillet. Cook, stirring often, until sauce is glazy and coats chicken and vegetables, and the chicken is cooked through, about 2 minutes. Transfer chicken and vegetables to a platter. Spoon sauce over. Top with toasted cashews.
Preparation Combine oyster sauce, vinegar, soy sauce, brown sugar, and 1 Tbsp. water in a small bowl; set aside. Heat 2 Tbsp. oil in a large nonstick skillet over medium. Add cashews and tilt skillet toward you so that the oil pools around cashews. Toast cashews, tossing and spooning oil over constantly, until cashews are golden brown, about 3 minutes. Transfer cashews to a small plate and let cool, reserving oil in skillet. Cut chicken into 1/2"-thick slices. If any slices are longer than 2", cut in half crosswise. Season chicken with salt and coat with cornstarch, tossing chicken to evenly distribute cornstarch. Increase heat to medium-high and cook chicken in a single layer in same skillet, undisturbed, until golden brown underneath, about 3 minutes. Turn and cook until other side is just opaque, about 1 minute. Transfer chicken to a plate (it won’t be totally cooked through; don’t worry as it will finish cooking in the sauce). Cook beans and onion in same skillet, tossing often, until beginning to soften and brown in spots, about 4 minutes. Add remaining 1 Tbsp. oil followed by garlic and ginger. Cook, tossing often, until garlic and ginger are softened, about 1 minute longer. Add reserved sauce and return chicken to skillet. Cook, stirring often, until sauce is glazy and coats chicken and vegetables, and the chicken is cooked through, about 2 minutes. Transfer chicken and vegetables to a platter. Spoon sauce over. Top with toasted cashews.