This is a great way to preserve an abundance of foraged mushrooms, or simply to make sure that the store-bought mushrooms in your refrigerator don't spoil before you get around to eating them.
Most mushrooms dry beautifully, not only retaining but even gaining flavor in the process. When rehydrated in hot water, their texture is almost identical to fresh mushrooms. Dried mushrooms can be stored for at least a year.
First, clean the mushrooms. Contrary to culinary myth, raw mushrooms do not actually soak up lots of water, and you don't have to skip washing them and get all of the dirt off with a brush.
Go ahead and wash them in water, scrubbing with a vegetable or mushroom brush as necessary. This will make your prep much easier, especially with species that have lots of nooks and crannies, such as maitake.
Depending on what seems easiest for the shape of the mushrooms, either clean them whole and then slice them, or vice versa.
Slice the mushrooms between 1/4 to 1/2-inch thick. The thicker the slices, the longer they will take to dry.
Arrange the cleaned, sliced mushrooms on the dehydrator trays, making sure that none of the pieces touch or overlap.
Dry them at 110F/43C until the pieces are crispy dry. This will take 4 to 6 hours for 1/4-inch slices, up to 8 hours for thicker slices.
Allow the dried mushrooms to cool completely before transferring them to glass jars. Cover tightly with lids and store away from direct light or heat.
To use dehydrated mushrooms, pour boiling water over them in a heat-proof bowl. Let them soak for 20 to 30 minutes. Drain, reserving the richly flavored soaking liquid for soup stocks and sauces. Use the rehydrated mushrooms as you would fresh mushrooms.