- Cut tops of green onions into 2" long pieces.
- Combine sauce ingredients in small bowl and stir thoroughly.
- Cut steak across the grain into thin slices, about ½" deep by 2" long.
- In bowl big enough to hold meat, combine egg whites, salt and water chestnut flour.
- Beat with chopstick until frothy.
- Add steak, and use fingers to coat each slice.
- In wok, heat oil to moderately hot.
- When ready, piece of coated meat will rise to surface immediately.
- Fry meat in small batches; drop in 1 slice at a time to avoid sticking.
- Cook until lightly brown, about 1 minute.
- Drain on Chinese strainer or paper bag.
- Remove all but 2 tbsp of oil from wok.
- With wok at medium heat, quickly stir-fry green onions and ginger for about 20 seconds.
- Add sauce; bring to boil on high heat while stirring.
- Add beef all at once, and toss with sauce until beef is hot and coated.
- Push beef out of sauce, dribble in cornstarch paste to lightly thicken.
- Serve immediately.