Make the Sauce: Heat vegetable oil in a saucepan over med-low heat, until hot but not smoking. Add ginger and garlic to the pan, stir for 30 seconds, and quickly add soy sauce and water.

Add brown sugar in the sauce, stir well, and bring to boil at medium heat for 2-3 minutes. Sauce should thicken a little. Remove from heat and set aside.

Slice flank steak against the grain into ¼ inch thick bite-size slices. To get nice cuts, tilt blade of knife at 45 degree angle.

Toss steak pieces into a large bowl with cornstarch. All pieces should be coated. Let beef sit for 20 minutes.

Meanwhile, heat vegetable oil in a large wok or skillet over medium heat until hot but not smoking. Add beef to the pan and stir frequently for 2-3 minutes or until beef browns on the exterior.

Remove beef with slotted spoon and place onto paper towel lined plate. Pour the oil out.

Add the beef back into the empty pan and stir over medium-low heat for 1 minute. If desired, add dried red chilies.

Add the sauce, cook and stir for 1 minute. Add green onions. Cook for 1 minute, stirring, until beef is fully cooked through and onions are wilted. Serve immediately over cooked rice.