Slice beef against the grain as thinly as possible and place in a medium bowl. It's easiest to slice/shave the beef if it has been placed into the freezer for a few minutes. Alternately, your butcher may shave it for you.
In a small bowl, whisk together the soy sauce, cornstarch, water and sugar. Add to beef and stir to combine. Set aside.
Heat a wok or large skillet until very hot. Reduce the heat to medium. Add 1 tablespoon oil; add onions and vegetables; stir-fry for 2 to 3 minutes. Don't let them brown. Remove the vegetables from the pan and set aside.
Heat the pan to high and add the remaining 2 tablespoons of oil, ginger and beef. Stir-fry until the beef pieces separate and just begin to change color. Add the cooked vegetables back into the pan; stir to blend. Stir-fry about 1 minute, being careful not to overcook.
Notes
Additional vegetable suggestions: broccoli, cauliflower, water chestnuts and green beans.
If you are preparing this recipe as GLUTEN-FREE, just be sure to use a brand of soy sauce that does not contain gluten.