So there’s this big controversy about washing mushrooms. I don’t quite understand, honestly. Some people think washing mushrooms will make them slimy, so they brush the mushroom to get any attached dirt off the outside. Other people don’t wash mushrooms because they expect mushrooms to absorb water, hence diluting the flavor of the mushroom. Alton Brown, of Good Eats fame has, in my opinion, debunked this “myth” of mushrooms. He methodically washed and soaked mushrooms, and was able to demonstrate they did not soak up much water: an increase from 4.0 oz to 4.2 oz, for an increase of 0.2 oz, 5% of their weight, or about a teaspoon of water. Mushrooms soak up a trivial amount of water when they’re washed. When I cook with mushrooms, I make sure to rinse off the dirt using the sprayer in the kitchen sink. However, mushrooms that have been washed need to be used – they can’t be washed and stored.
Mushrooms store poorly in the “fresh” state. Since mushrooms are made up of so much water, the dry climate of the fridge sucks their moisture out. I keep my shrooms in a tightly closed paper bag in the fridge. They seem to do okay for 4-5 days.
Since mushrooms are made up of so much water, drying them is a great way to concentrate their flavor and preserve them for a long time. I haven’t dried my own mushrooms, but I’m sure PFB has a chapter or two on the process. I have used dried mushrooms for a number of different dishes. Dried porcini have a wonderful flavor, and make a rich broth when reconstituted. Japanese dashi stock often uses dried shiitake mushrooms to add flavor. Cooks Illustrated is also enamored of using powdered dried mushrooms (usually shiitake) to thicken dishes and add rich “meaty” flavor.