In another bowl mix the first five ingredients with 1 tablespoon of the oil, pour over the beef and mix well. Let stand at room temperature and marinate for 10 minutes while chopping the vegetables.
In a hot wok put the remaining oil and red pepper flakes, cook until fragrant and add the beef. Stir quickly to sear and after several minutes remove from wok and set aside.
Add the vegetable to the wok and toss quickly to coat with beef juices and oil. Add the crushed garlic and cook for several minutes.
In a small bowl mix the stock and cornstarch. Pour this over the vegetables and toss to coat, sauce with thicken after a few minutes.
Add the beef back to the wok and quickly stir fry the dish to incorporate. Serve as is or over steamed rice.