Context: The collector asked the informant (as MD) for some Shanghainese folklores. The informant is the mother of the collector.
MD: You know, when a couple in relationship want to make sure parents from each side agree with their marriage, they will visit the woman’s mother. When it is the first visit for the man, he should bring gifts, such as liquor or cakes or whatever, while the future mother-in-law is supposed to serve him a bowl of 水潽蛋 (Shanghainese in IPA: /sɻ̩ pú de/ Chinese Mandarin in Pinyin: /shuǐ pū dàn/ Literally: water boiled egg, specifically poached egg in Shanghainese), 水煮蛋 （Mandarin in Pinyin: /shuǐ zhǔ dàn/, literally: water boiled egg）. The kind of water boiled egg that you break the shell first and then boil it. (The informant was emphasizing the difference between hard boiled eggs and poached eggs)
Collector: Yes, I got it. But why?
MD: I have no idea. It’s just a custom! If the woman’s mother does serve the man a poached egg, that means she recognizes the man as her future son-in-law.
Collector: Is there anything special with poached eggs? Aren’t they just daily matters?
MD: Well you know, life in the past wasn’t like now. Eggs weren’t something you could afford every day!
Collector: But you told me your family had hens when you were young… Okay, okay, I got it. Did Grandma serve Dad poached eggs when he first went to visit?
MD: She did.
Collector: Did she just give him the egg or she told him what that meant? Dad mustn’t know the custom. (The collector’s father is not from Shanghai)
MD: Well, she just served him the egg. Your dad is an outlander. He didn’t know.
Collector: Then did you tell dad what the egg meant?
MD: Yeah after the visit.
Collector: But wasn’t that meaningless for Grandma to do so? Because Dad couldn’t know what she implied.
MD: That doesn’t matter. It was the purpose and the feeling of the mother-in-law that mattered.
Collector: Alright. If CH (the collector’s elder sister) brings her boyfriend to you and you think he is a good man to marry, will you also serve him poached eggs?
MD: Yes, I will, if I like him.
Collector: Even if he is a foreigner?
MD: Yeah. That doesn’t matter.
In the past, eggs were valuable food for ordinary people. Even if they had hens, they would probably rather sell eggs for money than consume eggs frequently. Thus, serving future son-in-law eggs is sharing something highly valued with that person, meaning that the man is viewed as a trustworthy husband and is welcomed as a new family member.
It is interesting that the informant values this custom and intends to actively carry it on even though she didn’t really know the background of the custom and in fact, the social context has already changed a lot, which to a certain extent reduces the special value of poached eggs and the meaning of the custom.
The custom might only be a practice in Shanghai, but it’s also possible that the custom is practiced in a larger region, for example, the Yangtze River region.