[Raak] Continuing my clarification, the answer is a particular fungus, which has as its fruit (spore) an edible mushroom. I would guess that the mushroom is sold in some supermarkets, but I do not think it is commonly found for sale. (By the way, some of my reading has led me to the discovery that fungi are not necessarily classified as either animal or vegetable, but are a class on their own, so we may have to rename the game AVFMA.)

Oh, and it is highly unlikely that you or I would find the edible part for sale in a supermarket, but Dan or Dunx might.

[CdM] If you went down the AVFMA road, you'd have to add a couple of others to the list, too.

[flerdle] Mutually beneficial relationship with conifers? - Definitely not.

(But despite that, the audience applauds, somewhat confusedly.)

[Dujon] Medicine rather than food? - No.

[CdM] Many of your answers seemed to be pointing to the fruit of Tricholoma magnivelare, but that's obviously not right. Sorry.

[flerdle] Tm? - No, but in some ways you are getting very close.

[Irouleguy] Shiitake mushrooms? - No.

I'm thinking it can't be the cultivation of mushrooms on hardwood logs because you would've given a hint when I asked about trees some time ago - I still think this is some form of parasitic mushroom.