Yeah @Squidgy is right vegemite is really salty and that is the best and only description I can think of, and the trick is to use lots of butter with not too much vegemite, it evens out really well. Witchetty grubs are just white wood eating grubs that do not taste like chicken but are apparently supposed to and were used for ‘bush tucker’ 
by the aboriginals. 
These are witchetty grubs.