The Lantern Festival made in Beijing is mainly filled with stuffing. I've seen machines do Yuanxiao. First mix the stuffing, stir it evenly and spread it into a big round piece. Cool and cut into cubes smaller than table tennis. Then put the stuffing into a machine like a big sieve, pour in glutinous rice (called glutinous rice in the south) powder, and the machine will "sieve". As the fillings collide with each other and become spherical, glutinous rice also sticks to the surface of the fillings, forming Yuanxiao. The layer of Yuanxiao river noodles is very thin and the surface is dry, so the rice noodles absorb water and become paste when cooked in the pot.
Jiaozi in the south (Beijingers call it jiaozi according to Sichuan custom) is completely different, but it is a bit like Bao jiaozi. First, add water to glutinous rice flour and knead it into dough (just like Bao jiaozi), and let it "wake up" for several hours. Then mix all the stuffing materials and put them in a big bowl for use (don't cut them into small pieces like Yuanxiao). The water content of dumpling stuffing is more than that of Yuanxiao, which is one of the differences between them. The process of wrapping jiaozi is also like that of jiaozi, but there is no rolling pin. Wet glutinous rice flour is very sticky, so we have to pull a small group of wet noodles by hand and squeeze them into a circle. Use chopsticks (or thin bamboo tools) to pick a ball of stuffing and put it on the glutinous rice slices, and then turn your hands around to wrap jiaozi. The surface of the finished jiaozi is smooth and shiny, and some of them are pointed, like a peach. Dumpling skin contains enough water, which is sticky and difficult to preserve. It's better to cook and eat now. Now with quick-freezing technology, jiaozi appears in stores.
There are many "schools" of jiaozi in the south, and now the most famous one is jiaozi, the "Black Ocean Crisp" in Ningbo. The so-called "black ocean crisp" is a mixture of lard and black sesame powder, and lard is not boiled pure oil, so the original "plate oil" in pig stomach should be used. Tear off the omentum outside the "suet", squeeze it by hand, and then add the black sesame powder bit by bit. This thing is absolutely dross from the perspective of modern health preservation, and it tastes excellent: slippery, waxy, soft and spicy, and it is worth a try.
The softer and smoother jiaozi is, the better, so the raw materials of glutinous rice are very particular. Choose a variety with strong viscosity. There is also a saying in the processing technology that "water mill powder" should be used. That is to say, after the glutinous rice grains are soaked in water, they are ground with water (like soybean milk), preferably with a stone mill. The ground powder can be hung in gauze bags and drained, and can be refrigerated for three or four days (it will be sour after a long time). It can be seen that a good jiaozi is difficult for industrial production, which is another feature that distinguishes it from Yuanxiao.