"Bun bo originated in Hue, a former capital of Vietnam.
Outside the city of Hue and some parts of Central Vietnam, it is called bún bò Hue to denote its origin.
Within Hue and surrounding cities, it is known simply as bún bò.
The broth is prepared by simmering beef bones and beef shank with lemongrass and then seasoned with fermented shrimp sauce and sugar for taste.
Very spicy chili oil is added later during the cooking process.
Bun bo usually includes thin slices of marinated and boiled beef shank, chunks of oxtail, and pig's knuckles.
It can also include cubes of congealed pig blood, which has a color between dark brown and maroon, and a texture resembling firm tofu.
Bun bo is commonly served with lime wedges, cilantro sprigs, diced green onions, raw sliced onions, chili sauce, thinly sliced banana blossom, red cabbage, mint, basil, perilla, persicaria odorata or Vietnamese coriander, saw tooth herb and sometimes mung bean sprouts.
Thinly sliced purple cabbage is acceptable substitute when banana blossoms are not available.
Purple cabbage most resembles banana blossom in texture, though not in taste.
Fish sauce and shrimp sauce is added to the soup according to taste."