The steamed blood-filled dumplings were made with chicken and duck blood.
There was a mighty general called Wangdamosu, the uncle of Emperor
Kangxi of the Qing Dynasty, who defeated Li Zicheng and Zhang xianzhong
and was regarded as the first valiant fighter in the Qing Dynasty. Every
morning after attending the Court，he would rode on the horse back to run
a round around the city Beijing. Then he would go to Xidan to eat the
steamed blood-filled dumplings. These dumplings were specially prepared
for him. For while riding the horse, he would breath in a lot of dust and
dirt into his lungs. And the duck and chicken blood can help keep the lungs
clean. However eating animal blood was forbidden after the Japanese
occupied Noth-China. Since then the steamed blood-filled dumplings
were almost missing and few people make them now.