Heat the oil in a large pot over medium-high heat. Add the beef and cook until browned on all sides, about 5 minutes. Add the garlic and ginger and cook for 1 minute more.
Add the fish sauce, soy sauce, pepper, brown sugar, beef broth, lime juice, cinnamon sticks and star anise. Bring to a boil then reduce heat to low and simmer for 1 hour.
Strain the soup through a fine mesh sieve into a clean pot. Discard the solids.
Return the soup to a simmer and add the cooked noodles. Simmer for 5 minutes more before serving.