Winter Solstice is Dōngzhì (冬至) in Chinese. Dōngzhì festival has been celebrated for thousands of years. It is a time for friends and families to get together and mark the passing of time. Chinese people often make tāngyuán (湯圓), balls of glutinous rice with a sweet treat inside. They are often brightly colored and served in a bowl of sweet broth. Follow this link if you are interested in learning how to make tāngyuán.
Other traditional foods eaten on Dōngzhì Jié include lāmiàn (拉面) long stretched noodles symbolizing longevity and dumplings (饺子) stuffed with lamb to bring warmth to the start of winter.
Interestingly, most Chinese festivals are celebrated on a full moon. Only Spring festival is celebrated on the new moon. So it is interesting that they celebrate the Summer and Winter solstices. So unlike Western people they don’t start Winter on the day of the longest night, they mark it on the 22 full moon, and there is no celebration.