Siopao is a favorite Filipino snack, consisting of a meat filling inside a steamed rice-flour bun, a larger version of Chinese dumplings. It is usually sold as part of dim sum by Chinese-style restaurants such as Chow King and other dim sum shops (though like chop suey, the larger siopao (about the size of a McDonald's cheeseburger) is not traditional Chinese fare).
The two most common fillings are asado and bola-bola, although lots of others are possible, including chicken or vegetables. The bun is traditionally made from rice flour, not wheat - buns made with wheat flour are more commonly called asado rolls. The resulting bun is white, glutinous and sticky in texture; a square piece of wax paper or white paper is typically placed underneath while steaming, to prevent it from sticking to the bottom of the bamboo steamer.
Asado siopao is filled with diced pork or beef cooked in soy sauce (with salt and sugar added to taste); its taste and texture a bit like adobo. Indeed, a good use for leftover adobo is siopao filling (and most smaller food chains actually use leftover meat in this manner).
Bola-bola is a local term for Chinese-style filling; chopped pork and Chinese sausage baked with egg and flour to a consistency akin to meatloaf.
The cooked filling is placed inside the rice dough buns, and is allowed to rise for about half an hour before steaming for another half hour. If not consumed immediately, the siopao buns can be stored in the steamer (on low heat) for about half a day or so before going stale.
This the cliched pasalubong for the kids or the wife by office workers late for dinner. The bun is generally eaten with a sweet asado sauce (soy sauce and oyster sauce, simmered with brown sugar) - you can either poke a hole in the side and squirt the sauce in, or drip it onto the filling as you eat it. Some fastidious eaters pick the "skin" off the bun before eating (especially for siopao bought from roadside stalls).
Recipe taken from memory; there are some recipes on the net, but I notice they all list wheat flour, instead of rice flour, so I'm not so sure about the quantities.