In a large, heavy based stockpot heat half of the olive oil. Add the beef and cook until browned all over. Transfer to a plate and set aside.
Heat the remaining olive oil over medium heat. Add the onion and cook for 2 minutes, then stir in the carrot and celery for 5 minutes or until the onion is soft. Stir in the bay leaves, thyme, tomato paste and peppercorns. Cook for 2 minutes, then return the beef to the pan.
Pour the cold water over the beef and vegetables. Cover and bring to the boil, then reduce heat to low and simmer for 2 hours. Stir the brood di carne (beef soup) occasionally, skimming any scum that rises to the surface.
Remove the stockpot from the heat. Strain the beef soup through a fine sieve into a clean saucepan, using the back of the ladle to extract as much flavour as possible. Season the soup with salt to taste.
Note: The onion, carrots and beef can be served on the side or are perfect to make a pie the following day.
Place the saucepan with strained brodo di carne back onto medium heat. Bring to the boil. Add the tortellini, referring to the cooking time specified in pasta packet instructions.
To serve, spoon the tortellini among serving bowls and ladle hot brodo do carne over the tortellini. Top with Parmigiano Reggiano – buon appetito.