You are da man. I have got to get back on my mycology path. I was obsessed with it when I first moved to the woodsy home we live in now. I was like “there has GOT to be some varieties of mushrooms I can eat growing around here”. It was like that saying “water water everywhere but not a drop to drink”…I had shrooms everywhere! But knew there was danger.
Then I joined The Shroomery web site to learn…how to kill yourself with wild mushrooms! I did find many varieties and kept my deep fryer going for a few years on that tangent. I walk by them now and just make a mental note like “hey, beautiful puffball there…I used to eat those”! I used to ask random home owners to harvest mushrooms from their yard but had to interrogate them as to any chemicals they may have used. People got this puzzled look on their face “I can’t believe this stranger just asked for my yard mushrooms”! I would nearly wreck my car keeping an eye out for shrooms after a soft rain.
So back on topic:
The simple answer is "wash the mushrooms". Like others said here, there have been tests debunking the myth that “washing mushrooms is detrimental and that they are little sponges that will soak up that water”. I STILL see TV chefs saying this…it’s irresponsible for them to do so in my opinion because produce comes from all over, you don’t know what’s on them when you buy them. Heck they just discovered Mexicans were defecating in the cilantro fields down there…a good reason to grow your own.
America’s Test kitchen also did the test to debunk this heinous myth that has people spending all this time brushing shrooms or eating potentially dangerous unwashed shrooms. They soaked one batch, rinsed one batch and dried them on a towel then weighed them and compared to the unwashed control sample there was almost no change in weight, Mushrooms are essentially all water, the only ones that act like sponges are dehydrated or dried.
I do not buy sliced mushrooms. I don’t usually buy ANY pre-prepared vegetables. I prefer to cut my own. I refuse to buy bagged salad anymore as well; I can tell when I go to a restaurant and they are using bagged salad mix, I can literally taste it, plus there have been a whole lot of contamination cases over the years, those bags seem to be petri dishes and almost no-one is going to wash a salad mix before they eat it.
I would think you would have no problems washing sliced mushrooms either, if they are the meaty button kind. You’d have to be careful with big slices of portabella if you want them in whole slices to keep them from breaking.
With button and cremini shrooms, I wash them under running water using my hands to remove stubborn grow medium then lay them on a kitchen towel. Before slicing them for a salad for instance I pick each one up with the towel and use the towel to dry them off. Yes, we wash a lot of towels in Chef Kenny’s house…I’m old school like that. I did not learn that from momma, she won’t use towels or sponges, afraid of bacteria.
I do not wash mushrooms till I’m ready to eat them. I leave them in the little container they are sold in which is designed to let them breathe. If I buy bulk loose ones, I tuck a paper towel underneath of them and leave them in the bag they are in, with the top of the bag loosely crumpled together, not sealed.
During my mycology obsession and time on The Shroomery it was always advised that you not only wash wild mushrooms but you always cook all of them, every single type before eating. They advised to NEVER eat a raw wild mushroom of any type and that is AFTER you have 100% positively identified that you have a safe to eat shroom using spore prints, bruise testing and written and pictorial media and even a post and Q&A on The Shroomery where people who live for shrooms will tell you if you are good to go. If you don’t know what you are doing, do not eat wild mushrooms…period. Your mileage, danger level…and lifespan might vary!
Homegrown shrooms are safe, especially if you bought spore kits from a reputable dealer.