Sometimes a recipe for stock or soup will call for dried mushrooms. Drying your own is much cheaper than buying them that way at the store. I used 1lb white button mushrooms. Unless you are a mushroom aficionado and can tell the difference, fungus is fungus and these will give a dish that richly earthy flavor.
Brush any dirt off the mushrooms, but I don't wash them. Cut them in half. Place them cut side down on a cutting board and slice them vertically into 4 or 5 slices. Arrange the slices on dehydrator trays, using inserts for smaller pieces if necessary. They should not overlap, but they can be crowded since they shrink a lot. I dry these out at a medium temp for the first 12 hours to keep them from molding since they tend to start out damp. I lower the temp as they dry out. It takes at least 24 hours until they are thoroughly dry.
They can be stored in airtight containers in a dry dark place for a month or two. I also grind them into powder and use it in place of bullion powder when making soup broth.