In A Large Bowl, Mix Together The Ground Beef, Egg, Bread Crumbs, Pepper, Salt, Onion Powder, Garlic Powder, And Worcestershire Sauce. Form Into 8 Balls, And Flatten Into Patties. Heat The Oil In A Large Skillet Over Medium Heat. Fry The Patties And Onion In The Oil Until Patties Are Nicely Browned, About 4 Minutes Per Side. Remove The Beef Patties To A Plate, And Keep Warm. Sprinkle Flour Over The Onions And Drippings In The Skillet. Stir In Flour With A Fork, Scraping Bits Of Beef Off Of The Bottom As You Stir. Gradually Mix In The Beef Broth And Sherry. Season With Seasoned Salt. Simmer And Stir Over Medium-Low Heat For About 5 Minutes, Until The Gravy Thickens. Turn Heat To Low, Return Patties To The Gravy, Cover, And Simmer For Another 15 Minutes.