Step 1

Place the beef in the freezer 15 minutes before ready to begin. This will help firm it up for slicing.

Step 2

Slice the beef against the grain in thin, bite-sized strips, about 1/4 inch thick.

Step 3

Add the cornstarch to a Ziploc bag. Place the meat in the bag and shake, until well coated. Pour out into a strainer or colander and shake off the excess cornstarch.

Step 4

In a small sauce pan add the oil, soy sauce, brown sugar, garlic, ginger, water, rice wine vinegar and red pepper flakes. Stir and cook over medium-high heat until sauce thickens (15-20 minutes). Set aside.

Step 5

Meanwhile, in a large skillet heat the oil over medium-high heat. When the oil is hot, add some of the beef in a single layer and cook until browned. You will need to do this in batches. Set aside the browned beef on a plate lined with a paper towel and tented with foil.

Step 6

Return all beef to skillet and pour sauce over the beef. Stir until coated and cook for a couple more minutes.

Step 7

Serve over rice and garnish with green onions.