Every mushroom species now grows in five varieties. Each has its own name, its own colour and its own property: it restores Health, Stamina or Mana, sates Hunger, or takes Health away.
The five are dealt out afresh in every world, and each species is dealt separately. A Golden Fat Mushroom tells you nothing about a Moonlit Blightcap, and a legend learned in one world does not carry into the next.
A variety you have never eaten is named for its species alone, as Unknown Fat Mushroom, and its properties read as question marks. Eating one names that variety and reveals what it does, for that species alone. Brewing or cooking it teaches nothing. The Forager perk knows every variety of every species on sight.
A mushroom carries its virtue into the pot as well, so a good one strengthens a broth and a poor one turns it bitter. Learn the ones that grow near your claim before you come to depend on them.