It wasn't quite fungal, but Diamond Age had the Seed. The Seed grew any material/structure/device desired as opposed to the Matter Compilers and the Feed. We know that the Seed required tons of computing power to design and create, but the exact method of function of the Seed wasn't detailed. We do, however, know that it may have been nanotechnological as Nell had nanotechnology that her Mouse Army created to counter the nanites in the Drummers.