1 (1 pound) piece beef tenderloin For Marinade: 2 tablespoons soy sauce 2 tablespoon sugar 1 tablespoon medium dry Sherry 1 ½ teaspoons Asian sesame oil 2 teaspoons cornstarch For the Stir Fry: 1 ½ pound bok choy 2 tablespoons soy sauce 3 tablespoons medium-dry Sherry 1 teaspoon balsamic vinegar 1 ½ cups vegetable oil 1 tablespoon minced peeled fresh ginger Cut beef crosswise (across the grain) into ¼ inch thick slices, then cut slices into ½ inch wide strips
Make marinade and marinate meat-Stir together marinade ingredients in a medium bowl until sugar is dissolved. Add beef, tossing to coat and marinate 30 minutes to 1 hour.Blanch Bok Choy-Separate Bok Choy into individual leaves and halve crosswise, keeping stems and leaves separate. Cook steam in a large pot of boiling water 15 seconds, then add leaves and cook 15 seconds more. Drain in a colander, and then rinse with cold water to stop cooking and drain well.
Fry Beef-Stir together soy sauce, Sherry, and vinegar. Heat vegetable oil in a heavy skillet over moderate heat until a deep-fat thermometer registers to 400 degrees. Add beef to hot oil with tongs (discard marinade) and cook, stirring carefully, until slices separate, about 1 minute. Transfer beef with tongs to a colander and drain.Stir fry beef and bok choy
Reserve 3 tablespoons oil from skillet and discard remainder. Heat reserved oil in skillet over moderately high heat until hot but not smoking, then stir fry garlic and ginger until fragrant, about 30 seconds. Add beef, soy mixture, and bok choy and stir fry until sauce is simmering and mixture is just heated through, about 1 minute. Serve immediately.