Cool Shrooms
A slang term that actually began it's use in the early 21 century teens/early 20's. Popularized by the Kyoto's pop culture (Kyo-pop) of the time. Used to describe something or someone very nice, down-to-earth or stylish or all the above. Great. Dashing. Kakoii.

When your Japanese coworker studies mushrooms and you say 'cool shrooms' instead of 'cool beans'

A synonym mainly used like cool, sweet, awesome, splendid, amazing, delightful, hell yeah and like in Japanese kakoii, iketeru, subarashi etc.
Genki: Hey man, look at this umbrella made out of shiitake!
Hana: Oh cool shrooms, man!

Hana: "Hey Genki! I froze some shiitake for you!"

Genki: "Wow, really? Coolshrooms!"

Hana: "Yo Genki, I won the patchinko."
Genki: "Cool shrooms!"