Wipe your mushrooms off with a damp paper towel right before you’re ready to use them.
Many people are confused about whether or not to wash mushrooms before eating them. While there are rare times when running your mushrooms under water is okay (like when you’re preparing a soup or a one-pot meal and they’ll be in liquid as they cook), rinsing is not usually recommended.
Even the quickest rinse will leave your cap surface slimy and damp, and soaking them will cause them to engorge and compromise your flavor and texture.
Instead, wipe your mushrooms off with a damp paper towel right before you’re ready to use them. Don't prep them before it's time to cook, as you'll only contribute to the aging process and your mushrooms will not last as long. Sometimes they’ll just need a dry gentle brushing to remove any remaining dirt.