Love jade

Next time when you visit Tamsui, look for this, not the limes but the yellowish jelly, known as Ai-yu愛玉, love-jade, extracted from Ai-yu seeds:

This sweet summer treat is always served chilled, nothing more refreshing than 愛玉冰. How is it made? Well,

First, the fruits are harvested and cut open.

The seeds are collected into a pouch of cheese cloth,
then placed into a pot containing an appropriate quantity of water.
Milk the pouch a few times and let sit.
The gel quickly and magically solidifies.

The final product. Addition of lime is a recent adoption.

Very few know that 愛玉子 is indigenous to Taiwan. According to 連橫's 台灣通史 published in 1921:

"愛玉子：產於嘉義山中。舊志未記載其名，道光初，有同安人某居於郡治之媽祖樓街每往來嘉義，採辦土宜。一日，過後大埔，天熱渴甚，溪飲，見水面成凍，掬而飲之，涼沁心脾，自念此間暑，何得有冰？細視水上，樹子錯落，揉之有漿，以為此物化也。拾而歸家，以水洗之，頃刻成凍，和以糖，風味殊佳，或合以兒茶少許，則色如瑪瑙。某有女曰愛玉，年15，楚楚可人，長日無事，出凍以賣，飲者甘之，遂呼為愛玉凍。自是傳遍市上，採者日多，配售閩、粵。按愛玉子，即薜荔，性清涼，可解暑。"
Essentially, its discovery was purely accidental. To quench his thirst in one hot summer, a certain Hokkien merchant was getting a drink from a stream somewhere in Jia-Yi, when he saw that the surface of water seemed frozen. After drinking from it anyway, he had found it a delightful, really hit the spot. Upon close inspection, he found some sticky seeds in the water. And, as they say, the rest is history. 愛玉 was actually the name of his lovely 15-year-old daughter who, having nothing productive to do, began selling in public this cool stuff as part of the new family business. People loved it and called it 愛玉 jelly, and the name 愛玉 stuck.

The statement in the last sentence "...按愛玉子，即薜荔..." maybe incorrect, though. In 1904, 牧野富太郎 （T. Makino） published a paper and designated 愛玉子 as Ficus awkeotsang Makino (notice the Taiwanese pronunciation of the species name). He actually collected samples in the then 嘉義廳下打貓東頂堡生毛樹庄 (now 嘉義縣梅山鄉). A British botanist Corner was of the opinion that 愛玉 was very close but not identical to 薜荔 (Ficus pu-mila L.). Since classification of the latter had preceded 愛玉, 愛玉 is therefore re-classified as a variation of 薜荔, or Ficus pumila L. var. awkeotsang (Makino) Corner. [Just to nit-pick a bit more, the pronunciation of 愛玉 as a person's name in Taiwanese is Ai-G'kio, not Aw-G'eo. 連橫 should have known.]

Such a long history of Ai-yu in Tawian, it is therefore not too surprising to see this coffee shop in Yokohama, Japan, displaying a prominent sign of 愛玉子 - with the 片假名 pronouncing in Taiwanese, aw g'eo ji,presumably not to be confused with "(I) love eggs" or even a girl's name, Ai-g'ioku-ko.

横浜市中区黄金町２－６