Cut the beef into 1 inch square thin slices (across the grain). Put in a bowl and marinate with soy sauce, cornstarch, sugar, and cold water for half an hour at least (longer is better). Add 1 tablespoon of oil and mix well.
Slice the potatoes into diagonal pieces.
Heat 3 tablespoons of oil. Stir fry the onion. Add the curry powder, then carrot and po