1 3/4 lbs. flank steak, skirt steak or hanger steak, cut on the bias and against the grain
6-8 tbsp. lite soy sauce
2 tbsp. rice wine vinegar
2 tbsp. cornstarch
2-3 tbsp. peanut oil (you can use canola or vegetable oil, but peanut oil has a higher smoke point)
2 large onions, sliced thinly
2 large bell peppers, sliced thinly, any color
In a small glass bowl, mix 3 tbsp soy sauce, 1 tbsp water and about 1 tbsp. of the cornstarch. Set it aside.
In a wok or large frying pan, add in 2 tbsp oil and add the beef spreading evenly in the wok. Cook for 20 seconds without touching and letting the beef brown. Cook meat, turning and making sure to brown for another 2-3 minutes. You will have to add the meat in batches as it won't all fit. Don't crowd it because if you do, you will be steaming the meat and you don't want to do that. After each batch is done, set aside on a plate.
Add the remaining oil to wok, add peppers and onions and cook until onions and peppers are soft, about 7 minutes..Add the beef back into the work and then add the rest of the sauce. Stir everything together and let cook another 2 minutes until everything is all incorporated. Transfer to a serving platter. I served mine over white rice and steamed sesame broccoli.