1. Heat a 12-inch nonstick saute pan or skillet briefly over medium-high heat; add oil. Season the steak with salt.
2. When oil in pan sizzles, add the steak. Cook for 5 minutes; turn and cook an additional 4 to 5 minutes for medium rare. Remove steak from pan and keep warm.
3. Take pan off heat and add sherry. Return pan to medium-high heat and cook for about 1 minute, scraping up any browned bits from the bottom. Add the scallions, ginger and garlic. Cook for 1 minute.
4. In a small bowl, mix together beef broth, water, soy sauce, oyster sauce, vinegar, cornstarch and sugar. Add to pan and bring to a simmer. Simmer for 1 minute over medium-high heat until slightly thickened. Take off heat and allow to cool slightly.
5. Slice the meat against the grain and arrange over cooked rice. Drizzle a few tablespoons of the sauce over the meat. Serve the rest of the sauce on the side. Garnish with additional sliced scallions, if desired.