Washing Dried Mushrooms Before Grinding into a Powder
When a recipe calls for grinding dried mushrooms, should the mushrooms be washed first?
We often add dried mushroom powder to recipes that need a savory flavor boost. Because commercially produced shiitake mushrooms are grown in controlled conditions, they tend to emerge from packaging fairly clean and debris-free. Porcini mushrooms, on the other hand, are generally not farmed but foraged. Although they are harvested above the soil line, they vary in cleanliness. (Pieces with large pores tend to hold on to grit, so try to buy dried porcini that look smooth.)
Our advice for cleaning is the same as that of the chefs and mushroom foragers whom we consulted: Don’t bother washing shiitakes, but swirl porcini in a large bowl of cold water, lift them out of the bowl, and shake off the excess water. Microwave them at high power for about a minute to remove any dampness. (The mushrooms should be steaming hot.) Let the mushrooms cool for about 2 minutes and then grind them to a fine powder in a spice grinder.