Preparation: Cut Tops Of Green Onions Into 2" Long Pieces. Combine Sauce Ingredients In Small Bowl & Stir Thoroughly. Cut Steak Across The Grain Into Thin Slices, About 1/2" Deep By 2" Long. In Bowl Big Enough To Hold Meat, Combine Egg Whites, Salt & Water Chestnut Flour. Beat Chopstick Until Frothy. Add Steak, & Use Fingers To Coat Each Slice. Deep-Frying: 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. Stir-Frying: Remove All But 2 T Of Oil From Wok. With Wok At Medium Heat, Quickly Stir-Fry Green Onions & Ginger For About 20 Seconds. Add Sauce; Bring To Boil On High Heat While Stirring. Add Beef All At Once, & Toss With Sauce Until Beef Is Hot & Coated. Push Beef Out Of Sauce, Dribble In Cornstarch Paste To Lightly Thicken. Recombine. Serve Immediately.