Whisk together cornstarch and cold water in a small bowl. Reserve.
In a separate bowl, whisk together 2 tablespoons of the oil, ginger, tamari, low-sodium soy sauce, sesame oil, mirin, and red pepper flakes. Reserve.
Heat remaining oil in a large frying pan or wok over medium high heat until it shimmers.
Working in batches add beef to the pan, and sear for 2-3minutes, stirring occasionally until no longer pink.
Remove beef from the pan, and reserve on a plate.
Add the soy sauce mixture and the beans to the pan.
Reduce heat to medium, and cook until beans are bright green and crisp tender, approximately 3-4 minutes.
Add the beef back to the pan, and stir in the cornstarch slurry.
Stir until mixture is thickened, about 3-4 minutes.
Serve on cooked rice, or noodles.