Bánh ú tro, a pyramid sticky rice cake filled with green mung bean for the 5th of May festival (by Lunar calendar)
The strong smell that I call "stinky"surely comes from the "lye water" (nước tro) or sodium bicarbonate, it makes "bánh ú tro" unlike any other cake wrapped in leaves. I don't know why we need that smell but without it - we will never call "bánh ú tro", where the last word "tro" means "ash". I think there is a lot of "sodium and potassium" there!
Bánh ú tro filled with green mung bean or with red bean, before - no fillings.
Bánh ú tro or bánh gio (gio - another dialect of "tro", I guess) is not the cake that we can buy for year round, we see it only a few days before the 5th of May by Lunar calendar or few days later and that's all. We call this special day - Đoan Ngọ festival or the insect festival, when the farmers used to celebrate the good harvest as a lot of insect has been killed. By tradition the farmers should prepare this cake for the offerings within the mid of "Horse hour" (from 11:00am to 13:00pm), that's why we have a name "Đoan Ngọ" (mid of Horse hour!)
This small in pyramid shape cake wrapped in bamboo leaves, always in dozen, it means you should buy a dozen as minimum. It could be too much for a person who just want to taste a small bite - like me yesterday. I got a dozen - I finished only three pieces. No one in my family seems like it, so I gave it away.
Nowadays easy to find bánh ú tro with filling, either with green mung bean or red bean, a bit sweet and tasty, much better than a cake with nothing, no sweet, no salty. I think the sweet filling has been added not long ago, because when I was kid, no way to find any "bánh ú tro" with filling!
We have various specific cakes for different traditions, like "bánh chưng" or "bánh tét" - a special sticky rice cake for Lunar New Year, this cake for the 5th of May festival or many other forgotten traditional cakes related to our old agricultural lifestyle and we, the urbanist, adore the technology, the science and gradually ignore the tradition, the belief that has been rooted in our culture for long.