YenSao is Swiflet Nest. You can get more information on those link1 & link2
Yến sào(Bird's net): Món ăn vua chúa
Yen sao ( birds nest) ( swallow nest)
We could sale YenSao from VietNam( Nha Trang, Hoi An, Qui Nhon) to you. You can have the best taste of YenSao's soup when you are in VietNam. Contact us for more information on Bird's nest when you are interesting.