The porcini, Boletus edulis, is a mycorrhizal fungus- it needs to establish itself with a tree host to fruit. They prefer natural woodland areas with older trees- I think it takes quite a few years before they will start fruiting. So far they can't be cultivated, sorry :(

That said, if you have the right kind of trees and climate, you could always try spreading spores around them, and waiting for the trees to mature to see if they grew :)