it's crafted at a crafting table with a bowl 2 mushrooms and a red mushroom still don't know how to get a red mushroom yet though it's called like strange stew or something like that if you know how to get the red mushrooms please tell tried the wiki but all the pages are just empty or dead links

To get the red mushroom, and many other consumables, you need to craft a hoe and watering can. you can hoe dirt and plant 'strange spores' on the hoed dirt. you then need to water it and wait for it to grow. once its matured, you hover your cursor over it and it will say 'ripening' which you then can mine to get the red mushroom. You can plant a lot of seeds and they give you various buffs.

there is no such thing as the watering can currently. The only way for the shrooms to grow is through naturally occurring rain. That's what worked for me at least.