In a small bowl, combine the green onions, cilantro and onions together. Season the vegetables with salt and pepper. When the broth is ready, remove and discard the oxtails and bones. Reserve the tripe, flank steak, and brisket. Strain the broth into a clean pot through a strainer with a double layer of dampened cheesecloth. Add the fish sauce to the broth. Bring to a boil and reduce to a simmer. Slice the tripe, flank steak, and brisket, into small pieces. In a pot of boiling water, drop inthe drained noodles and remove immediately and drain. Mound the noodles in the center of an oversized bowl. Arrange the meats on top of the noodles. Bring the broth to a rolling boil and ladle the broth over the meat. Garnish the soup with the green onions/cilantro/onion mixture. Serve the remaining ingredients along the side of the soup.