Oil cake is a traditional snack in northern China. It is widely distributed in Shaanxi, Gansu and Ningxia. It is a kind of pastry that is fried and has an elliptical shape. The filling is usually brown sugar or white sugar. The bubble oil cake is golden in color, delicate and soft, and does not change color after a long period of time. It tastes sweet and soft, and is a pure natural green food.