Rafter Sass showed us how easy it is to cultivate your own mushrooms!
Take Wood Chips/Straw/Natural Substrate (1 bale straw) soaked in water overnight (or mason's lime) and let it drain until it's spongey wet like good compost, then
mix the substrate with grain spawn (1lb) and pack it into cardboard boxes that are
taped shut and kept in a space 65-75 degrees. In 2 weeks, punch holes.
In 2 more weeks (or less?) you'll get mushrooms! Mist it after it fruits, and you should get 2-3 more flushes of mushrooms!
You can order "grain spawn" (grain that's been fully inoculated) here.