Recreational weed is illegal in Ireland.

You can order shroom spores online in most US states, they are not considered controlled substance since they contain no psilocybin. Get yourself plastic bag of sealed instant rice at the grocery store and get some micropore tape at the pharmacy. Then, inject the spores into the instant rice package (the spores should come in a syringe, shake it up well before injecting), seal the injection hole with micropore tape (it keeps out bacteria while allowing the growing mushroom mycelium to get the oxygen it needs to live, feel free to poke multiple holes and seal them with micropore tape as well for better gas exchange). It might take a week or two to start seeing mycelium growth in the instant rice bag, but as soon as you do, shake the bag vigorously to help distribute the mycelium around the bag (this helps it establish itself faster and outcompete any bacterial/fungal contaminants that may be present). Then wait another week or so (until the contents of the bag are firm to the touch and your view through the clear plastic part of the bag is entirely filled with white mushroom mycelium).

Next, buy some coco coir from a store that sells gardening supplies (it’s ground up coconut husk, apparently the mushrooms love it, and I’ve had success with it). Boil it in way more water than you think you’ll need (it nearly overflowed💀), and let it dry/cool down then pour that shit into a plastic tub. Get your fully colonized instant rice bag, open it up, and inspect it for contamination (anything blueish, greenish, or generally different in texture or color from the firm, white mycelium of the shrooms). If anything looks weird, cut it out from the block of mycelium. Then, break the mycelium into small chunks and bury the chunks in the tub of coco coir. You’re gonna want to get the ratio of coco coir to mycelium/rice in the tub no greater than 2 or 3 to 1 (if the mycelium has to travel too far between nutritious clumps of rice it won’t colonize the whole tub and contaminants will fill the empty space). Once you’ve got that done, you can pretty much just wait. As long as it’s in the 70s F and moderately humid in the tub, it’ll grow mushrooms within a week or two. You can shine a light on them during the daytime once the mycelium has colonized the whole tub to make it fruit slightly faster if you want.

Once it’s fruiting, harvest it, and don’t hesitate to mist more water into the tub if the mycelium starts to look dry. You can actually get like 4 or 5 harvests out of a tub and for a large enough tub, that can be a substantial amount of mushroom. Once you’ve harvested about that many times (or sooner if it gets contaminated or starts to look unhealthy), bury it outside on dirt and check up on it occasionally, sometimes it’ll fruit a few more times in the dirt.

Don’t kill yourself accidentally growing the wrong mushrooms. Yes sterilize your growing medium. But better, look up the uncle bens (rice) method for growing mushrooms. Shits easy.

Edit; Basically Gh0st’s post.

Mushrooms grow in shit. How sterile do you want it?

I mean, I’d get a bag of the same stuff you’d get for a vegetable garden. Also, be choosey with any fertilizer. You don’t want to be adding chemicals to something you’re gonna ingest.

I’m betting you can find some good books on gardening and mushroom farming at the local library (if those exist where you are). You’re gonna get a MUCH better result in anything you do if you learn about it instead of just winging it.