Bring chicken stock to a boil on medium high in a large pot.
Add in pastina or orzo and cook for 5 minutes.
Crack the eggs into a measuring cup with a lip and whisk them until broken up.
Bring the soup to a rolling boil, whisk the soup while you very very slowly drizzle in the egg, ensuring that you whisk continuously through the egg as it hits the soup.
Continue to cook the soup until the pasta is tender and then stir in the black pepper and scallions.
Divide the soup between the bowls and top each bowl with the parmesan.
