PREPARATION:
- For marinade, combine egg yolk, soy sauce, sherry and sugar in large bowl. Add meat; stir to coat well. Cover and refrigerate 1 hour, stirring occasionally.
- Drain meat, reserving marinade. Measure 8 tablespoons cornstarch into large bowl. Add meat; toss to coat well. Set aside.
- Drain pineapple, reserving syrup. Add syrup to reserved marinade with vinegar and tomato sauce; set aside. Combine remaining 2 tablespoons cornstarch and water in another small bowl; mix well. Set aside.
- Cut cucumber in half lengthwise; remove seeds. Cut cucumber into 1/4-inch pieces; set aside.
- Heat 3 cups oil in wok or large skillet over high heat to 375°F. Add 1/2 of meat. Cook until no longer pink in center, about 5 minutes; drain on paper towels. Repeat with remaining meat.
- Heat remaining 3 tablespoons oil in wok over high heat. Add vegetables; stir-fry 3 minutes. Stir cornstarch mixture. Add to wok with pineapple syrup mixture; cook and stir until sauce boils and thickens. Add meat and pineapple; stir-fry until thoroughly heated. Garnish, if desired.
