Huhu and Witchetty grubs are broadly similar, both being the tree dwelling, wood eating larvae of an insect. However the Huhu grub is a lot smaller than the one shown in Shauns picture, and is the larvae of a beetle, not a moth.
The beetles themselves are bloody annoying, and have a strong bite with their pincers. A bit like an airborne stag beetle.
Huhu grubs taste similar to peanut butter, a nice nutty flavour