3. Step
Heat the remaining 2 tablespoons canola oil in the pan. Add green beans and cook, stirring occasionally, until slightly charred and tender, 4 to 6 minutes. Add scallion whites, garlic and ginger; cook, stirring, until fragrant, about 1 minute. Add the vinegar mixture, reserved beef and remaining 1/4 teaspoon salt; cook, stirring, until well coated, about 1 minute. Serve sprinkled with scallion greens, if desired.