In a large soup pot, combine broth, onion, ginger, lemon grass, cinnamon, and peppercorns. Bring to a boil, reduce heat, and cover. Simmer for 1 hour.
Arrange bean sprouts, mint, basil, and cilantro on a platter with chilies and lime.
Soak the noodles in hot water to cover for 15 minutes or until soft. Drain. Place equal portions of noodles into 6 large soup bowls, and place raw beef on top. Ladle hot broth over noodles and beef. Pass platter with garnishes and sauces.