Welcome to my world. *sigh*
I've been pulling mushrooms/toadstools out of my raised veggie bed for two or so months. I think they're sprouting from the "rabbit waste" I put in w/o composting.
I believe I misunderstood how to use the rabbit waste: I received rabbit manure, used litter, and timothy hay from a rabbit rescue and mixed this all in with my other planting ingredients. Could be that manure by itself would have been OK, but the litter/hay are probably a source for the fungi sprouts. I took a couple to my local independent garden store and was told, by the woman with the recent hort degree, that she couldn't tell me which variety of fungus it was, but that its presence showed that I had "lots of organic material" in my planting medium.
I already knew that. *sigh* again
I just pull them out, making sure to get as much root as I can, and throw them into my yard waste.
I do NOT put these into my compost; I don't know whether they're poisonous and have no interest in finding out, AND I sure don't want to give them even more ideal conditions for growth.
USDA Zone 9, Sunset Zone 17