Before drying, oyster mushrooms should be clean and free of any debris. A brush will remove grit and dirt; wet mushrooms are slimy to handle so it’s not a good idea to rinse them under the tap. Many oyster mushrooms grow too large to be dried whole. Instead, each mushroom is carefully cut into strips about one-eighth inch thick. This also makes them easier to store and use when cooking.
An oven set to a very low temperature will dry out oyster mushrooms effectively. The mushrooms are spread in a single layer, either on a wire rack or on a clean dry baking sheet, allowing the warm air to circulate around the mushrooms. Drying requires about an hour at about 150 F. Once dried, the oyster mushrooms will shrivel up to a much smaller size.
If you live in an arid climate or find yourself with a batch of mushrooms during a hot weather spell, air drying may work for you. However, this method doesn’t apply in overly humid or cool conditions. In the right conditions, the mushrooms will dry up and become shriveled when set out on a wire rack in a single layer and left out of direct sunlight for around three days. An airing cupboard also works well if very dry and warm.
Dried oyster mushrooms are easy to use in cooking. There’s no need to soak and rehydrate the mushrooms; just drop a handful into whatever dish you’re preparing. If you do choose to rehydrate the mushrooms in a few tablespoons of water, the liquid can make a useful soup stock or flavoring for sauces and stews.