In a 10-in. skillet over medium heat, in hot cooking oil, cook onions 2 minutes, stirring occasionally. Add soy sauce, sugar and 1-1/2 cups water; heat to boiling. Reduce heat and simmer, uncovered, 15 minutes or until onions are tender.
In a cup, stir cornstarch and 3/4 cup water until blended. Gradually stir into onion mixture cook, stirring constantly, until sauce is thickened; keep warm.
Meanwhile, in medium bowl, mix beef, salt and pepper; shape into 4 patties. Cook patties as you would normally, in broiler or in skillet.
To serve, spoon onion mixture on top of each patty as a gravy. May also spoon over hot rice.