What is Garum?

The term "garum" is used to describe sauces made from fermenting seafood, animals or vegetables with salt and koji rice (the Japanese name for grains inoculated with the fungus Aspergillus oryzae). 

Most frequently, garum is used with fish and seafood as the Western equivalent to the Asian fish sauce (but tastes very different).

There is a great mushroom garum here which Liv used in her starter "Justice 97" for Great British Menu