Sesame doughnuts or sesame balls, jin deui in Cantonese, are a kind of Chinese fried pastry made with glutinous rice flour and frequently served at yum cha. They're ball-shaped and traditionally covered with sesame seeds and filled with lotus or red bean paste. Chef Lui's version has a custard filling - a delicious influence from Hong Kong. The custard needs to be made first for it to set and chill; this can be done the day before. The pastry is made with glutinous rice flour and wheat starch (tang meen fun in Cantonese) to create the viscosity that is the characteristic of this doughnut.
Note Wheat starch and glutinous rice flour are available from Asian grocers.