Trim fat from pork; discard. Cut pork crosswise into 1/4 inch thick slices. Place cornstarch on waxed paper. Coat both sides of pork with cornstarch. Reserve remaining cornstarch. Set asideCut onions into 1 inch pieces. Thinly slice ginger. Stack ginger, a few slices at a time, and cut into fine strips. Finely chop garlic. Set aside.Heat the wok over high heat about 1 minute or until hot. Drizzle 1 tablespoon oil into the wok and heat for 30 seconds. Add half of the pork and stir fry until well browned on both side. Remove the pork to a plate. Repeat with 1 tablespoon oil and remaining pork. Reduce heat to mediumAdd remaining 1 tablespoon oil, ginger, garlic, and onions to the wok; stir fry 1 minute. Stir in reserved cornstarch. Add sherry, soy sauce, 1 tablespoon water, sugar, and red pepper. Cook and stir until sauce boils and thickens. Stir in additional water if necessary.Spoon sauce over pork until coated and glazed. Sprinkle with cashews.Serve with rice. Garnish if necessary.