Fish salt is the bi-product of fish sauce. It's procured from the barrels of aging fish sauces and is really concentrated and savory. We use it at the restaurant to sneak in savory notes to dishes. It's incredible with lime juice and a little palm sugar as the base for a raw cabbage salad to go with fried fish or grilled pork. Works really well with nicely acidic dishes or charred foods with pickley and bright sauces.