Actually seen someone grow (regular, culinary) mushrooms off of these yellow blocks. They were definitely oyster types, but don't ask me which, or which color. The memory's gone.

What wasn't gone from my memory tho, was the size and time it took to grow. Like, I saw them prepare those blocks one night. Next day.... Nothing. The day after, still nothing visible.

Then I actually slept there, and the morning after.... Like, man... I was actually scared when I first saw it. The sprouts or whatever... They were bigger than my hands. And I have pretty big, pianist hands. A single night and the whole thing just... Just... jutting out off the side, as if a hole had been there all along. And then they grew more and more over the next three days. The full thing ended two times the size the yellow block, and at least larger than its original volume.