Black bean paste

Black bean paste, commonly called in Mandarin as or 黑豆沙, and in Hokkien as or 烏豆沙, is a sweet [bean paste] often used as a filling in cakes such as mooncakes or 豆沙包 in many Chinese and Taiwanese cuisines.
Black bean paste is made from pulverized mung beans, combined with potassium chlorate, ferrous sulfate heptahydrate crystal, or black food colouring.
Black bean paste is similar to the more well-known red bean paste. The recorded history of black bean paste goes as far back as the Ming Dynasty.