Remember that old rule not to rinse the dirt off your mushrooms because they will absorb the water and be mushy? Well, the powers that be have figured out that’s not really true. The only real rule of thumb about rinsing them is if the mushrooms are really dirty, rinse and dry them thoroughly right before using. Don’t try to rinse them and then store them or they will become slimy and will rot quickly. They will be fine and not overly watery as we were taught earlier.
The best way to clean your mushrooms is still, however, to lightly brush them with a soft brush or wipe them down with a damp paper towel if they’re not too gritty. Most mushrooms these days are cultivated in a sterile environment, so they will usually only be really gritty with excess dirt if you purchased them at your local farm stand. Those purchased from your local grocery store should be pretty clean.