Combine broth, oyster sauce, and cornstarch in a small bowl; stir until smooth. Beat egg with egg white in a separate small bowl. Set aside. Heat the wok over medium high heat until hot. Drizzle oil into the wok and heat 30 seconds. Add shrimp and garlic; stir fry 3 to 5 minutes or until shrimp turn pink and opaque. Stir broth mixture until smooth; add to the wok. Add onions. Stir fry 1 minute or until sauce boils and thickens. Stir eggs into the wok. Stir fry 1 minute or just until eggs are set. Serve over hot cooked Chinese egg noodles.