Yondu is a naturally brewed seasoning from Sempio, the company that makes the best Korean soy sauce. It has no MSG, and is used as a replacement for MSG. It gives wonderful umami flavor to food! Also, it is vegetarian! It is an optional ingredient in my recipes, but it makes everything taste better. You can find it at a Korean supermarket; it should be in the soy sauce aisle. Even though it is Korean, I use it for other Asian cooking as well, and can even be used for western cuisine! I get the green bottle, which is used differently than the orange bottle.