Cut each zucchini crosswise into thirds. Cut pieces lengthwise into slices Heat the wok over high heat about 1 minute or until hot. Drizzle oil into the wok and heat 30 seconds. Add zucchini and stir fry 8 minutes. Remove zucchini to medium bowl. Add the beef to the wok and stir fry until well browned. Add onion and garlic; stir fry 1 minute. Reduce heat to medium. Add basil and cinnamon; mix well. Stir in tomato sauce; cover the wok and simmer 5 minutes. Mix sour cream and egg yolk in a small bowl until well blended. Skim off excess fat from beef mixture. Spread beef mixture to an even layer. Arrange zucchini in single layer over beef mixture. Spoon sour cream mixture in center of zucchini. Cover; cook 5 minutes or until top is set. Sprinkle with cheese. Remove from heat; let stand 1 minute. Serve with orzo, if desired.