Wash the sweet potatoes thoroughly, peel them, and boil or steam them.
Mash the cooked sweet potatoes and mix in sugar, salt, and milk to form a dough.
Add glutinous rice flour to the dough and mix well.
Divide the dough into appropriate portions and shape them into balls.
Heat cooking oil in a pan and cook the dough balls over medium-low heat, turning until golden brown on both sides.