Gua bao

Gua bao (), also known as pork belly buns, ambiguously, bao, or erroneously as the bao bun ("bao" means "bun" so the translated name "bun bun" is redundant, and "bao" in the Chinese language without any qualifiers is generally used to refer to baozi) is a type of lotus leaf bun (). 
It consists of a slice of stewed meat and other condiments sandwiched between flat steamed bread known as lotus leaf bread. The lotus leaf bun is typically in size, semi-circular and flat in form, with a horizontal fold that, when opened, gives the appearance that it has been sliced. The traditional filling for gua bao is a slice of red-cooked pork belly, typically dressed with stir-fried suan cai (pickled mustard greens), coriander, and ground peanuts.
History.
In Asia.
The gua bao originated from the coastal regions of Fujian province in China. It is said to have come from either the cities of Quanzhou or Fuzhou. In Quanzhou, gua bao is known as rou jia bao (meat between buns) or hu yao shi (tiger bites lion). The custom of Hui'an people in Quanzhou is to eat these pork belly buns to celebrate the marrying off of a daughter. 
In Taiwan, gua bao were said to be introduced to the island by Fuzhounese immigrants. The food is known colloquially in parts of Taiwan as "hó͘-kā-ti" () in Taiwanese Hokkien due to the mouth-like form of the bun and the contents of the filling.
In Singapore, the dish is popular among the Hokkien community, where it is known as kong bak pau (炕肉包 "khòng-bah-pau").
In Hong Kong, they are known as cha bao () which means "fork buns" as the sandwiches are usually pierced by a toothpick or wooden skewer to keep the fillings in place.
In Japan they are called kakuni manju ()and are sold as a Chinese snack food. They are a specialty of Nagasaki Chinatown, having been sold in Japan for centuries due to the large number of Fuzhounese immigrants and historic relations between Fuzhou and Nagasaki represented by the construction of Sofukuji Temple. Recognizing the Fuzhounese community and historical connection, Nagasaki and Fuzhou established ties as sister cities in 1980. Another iconic Nagasaki dish of Fujianese origin is champon.
In the West.
Gua bao became popular in the early 2000s in the West through chef David Chang's Momofuku restaurants (c. 2004) although he says that he was unaware that the gua bao dish already existed because his Momofuku recipe was inspired by his dining experiences in Beijing and Manhattan Chinatown's Oriental Garden where the Peking duck was served on lotus leaf bread rather than the traditional spring pancake and he called them pork belly buns. The name "gua bao" was used and popularised by chef Eddie Huang when he opened his BaoHaus restaurant (c. 2009).
In the United States, New York City has a significant population of Fuzhounese Americans and gua bao is a popular dish sold at restaurants along with other iconic Fuzhounese dishes such as Fuzhou fish balls and lychee pork.
In the United Kingdom, they are often called hirata buns, named after Masashi Hirata, the executive chef of Ippudo in New York as many ramen restaurants began to adopt the practise of selling gua bao alongside their ramen dishes due to the influence of Momofuku and to meet high demand from customers who mistakenly believed they were a staple of ramen restaurants.
There have been many new trendy "gua bao" which incorporate pan-Asian fusion or non-Chinese stuffings between the lotus leaf buns, such as kimchi or karaage. Although these are technically not gua bao at all as they do not include pork belly, and in China would only be considered different lotus leaf bun sandwiches (he ye bao).