I would say freezing it will be the best method for preserving it indefinitely. When you thaw it out, it might be a messy goo, but at least the psilocybin will be intact. You might have to throw it in a smoothie or something to eat it at that point.
You could also dry it out. Try slicing the truffles, and spreading them out to dry. Once they are quite dry, put them in a container with some dessicant to pull the last bits of moisture out of them. Make sure the truffle slices never physically touch the dessicant, or they will absorb some of the chemical and they will become inedible. After they are bone crispy dry, store them in a cool dark and bone dry place.
Mycophile: I don't know anything about this variety of truffle, but I'm quite certain they will simply contain good old psilocybin.