Who is jiaozi eaten on the solstice in winter to commemorate?

People eat jiaozi in memory of Zhang Zhongjing, a "medical sage".

One winter in Zhang Zhongjing's later years, he saw that many people's ears were rotten with cold, so he began to study how to keep out the cold and made a soup called "Quhan Joule Soup". Mutton is the main ingredient, and some cold-expelling drugs are added to make soup. And the boiled mutton is salvaged and cut into pieces. It looks like ears with a noodle bag, and ordinary people don't get frostbite after drinking soup.

Zhang Zhongjing was a famous physician in the late Eastern Han Dynasty. He traveled to many places, collected different medical prescriptions, and wrote Treatise on Febrile Diseases, which made great and outstanding contributions in the field of prescription science and was highly praised and valued by medical workers.