is a Chinese-influenced stir fried noodle dish that is commonly eaten in Laos and Thailand. It is also quite popular in Thai and Lao restaurants around the world.
The name of the dish translates to "fried (with) soy sauce" and it is very similar to the char kway teow of Singapore and Malaysia. Phat Si Io is normally stir fried dry while another similar dish, rat na (in Thai) or lard na (in Laos), is topped with a sauce and generally has a lighter taste.
It is made with dark soy sauce ("si-io dam"), light soy sauce ("si-io khao"), garlic, broad rice noodles, called "kuaitiao sen yai" in Thai (commonly abbreviated to just "sen yai" meaning "big strip"), Chinese broccoli, egg, and some form of thinly sliced meat — commonly pork, chicken or beef — or shrimp or mixed seafood. The name comes from the soy sauce used in the dish, which is called "si-io", or "si-io" sauce, a loanword from Teochew. Phat Si Io is sometimes called "Kuai-tiao Phat Si Io" which reflects the general practice of using flat rice noodle as the main ingredient. However, other types of noodles may also be used.