As far as I know you can't practically create an alcoholic beverage from them without adding other things due to the low carbohydrate content, at which point you're really making it from the other things with the mushrooms for flavour. But fantasy fungus can have specific properties to make it possible!

I hadn't really considered what specific denizens the place might have. Mostly I just like dungeons to have some sort of basic ecology and food is always important so I went with that. Waldronate's comment does lead to another idea someone might want to use though - where do the denizens dump all the waste and rubbish?

Sadly there aren't many jobs in Mycology.