These soft buns are made by fermenting a flour and water-based batter that is then stuffed with fillings and steamed. Fillings normally include pork and onion, with some shops also adding finely chopped vegetables such as takenoko (bamboo shoots) or dried shiitake mushrooms. They are said to date back to the period following the Meiji Restoration, when Chinese steamed buns that had been introduced to Chinatown were adapted to fit Japanese-style tastes.

They were nominally “meat buns” but could not be sold under that name in the Kansai region; complaints would surely follow since “niku” (meat) in Osaka refers exclusively to beef. And since this dish features pork rather than beef, the dish is referred to in this region as butaman (pork buns).
One well-known chain has opened stores throughout the Kansai region, selling as many as 170,000 buns a day. Osaka is home to an ample number of butaman specialty shops featuring all manner of steamed buns. Some are heavy and bursting at the edges with fillings, while others are miniature-sized and thin-skinned.