Believe it or not, there is a tool designed just for this purpose. It is a small brush containing soft bristles and is appropriately called a mushroom brush. These brushes are easy to find at most kitchen supply stores and make cleaning mushrooms a breeze. Simply brush the mushroom off with the brush to release any dirt or sand, and trim the stem ends with a paring knife. You can also use a damp paper towel and gently rub off any dirt. Mushrooms should always be cleaned dry if at all possible—their spongy nature will cause them to absorb water if washed.