I got my hands on a German gardening magazine that
suggested/demonstrated growing oyster mushrooms in coffee grounds.
Can't read the german but would getting an oyster mushroom and letting
it rot (or shaking it over the grounds) be sufficient to get some spors
in?

Also suggested/showed shiitakes grown from oak and someother hardwood
logs. We only have poplus or various confier woods handy here. Also a
matter of getting the shiitake spores.