Bring broth to a boil over high heat in large saucepan; reduce heat to medium and simmer. Blend soy sauce and cornstarch in cup until smooth; stir into broth. Cook and stir 2 minutes, or until soup boils and thickens slightly. Stirring constantly in one direction, slowly pour egg substitute in thin stream into soup. Ladle into soup bowls. Sprinkle with onions.