Short and squat with a deep brown color, porcini mushrooms provide a meaty texture and savory umami bite to dishes -- from stews to risotto to pasta. Porcini also go by the names "cep" and king bolete and belong to the genus boletus edulis. Commonly used in Italian cuisines, porcini, which can be hard to find fresh, are often sold dried. When you use dried porcini, soak them first to make them pliable and flavorful.
Preparing to Soak
Dried porcini are available whole, sliced or in pieces. Portion out the amount you need for a recipe and soak them in hot water for at least 15 minutes. If they still feel a bit woody or tough after 15 minutes, give them up to 30 minutes. You could also soak them for several hours in room temperature water, which may preserve more mushroom-y flavor in the actual porcini. Once rehydrated, clean the mushrooms thoroughly to remove any grit. Opponents of rinsing rehydrated mushrooms say that this step diminishes their flavor, but gritty dirt residue will certainly ruin your dish. Add rehydrated porcini to mushroom risotto or to a braise made with lamb shanks or beef short ribs. You could also use the rehydrated mushrooms along with fresh white button or other wild mushrooms in a ragu for pasta.
Preserving the Liquid
Soaking porcini mushrooms yields a rich liquid that enhances the flavor of soups and sauces. Once you've removed the rehydrated mushrooms, strain the liquid through a fine sieve or a coffee filter to remove any grit residue. Add the liquid directly to sauces, stews, soups and braises, or freeze for future use.
Dried Versus Fresh
Dried varieties tend to have a stronger flavor than fresh. Substituting dry for fresh in some recipes can work, as long as you account for the more intense flavor by moderating the amount used. Fresh porcini rarely have the same concentrated flavor as dried and shouldn't be used as an alternative.
If you luck upon fresh porcini when they're in season, usually late spring or fall, buy extra and dry them yourself to reheat when fresh aren't available. Use a dehydrator or a low oven set to a temperature of about 150-degrees Fahrenheit. Clean the fresh mushrooms thoroughly using a soft brush or cloth. Do not use water as the porcini soak up the liquid, compromising the dehydration process. Slice the mushrooms relatively thinly, as this will hasten the drying process. Spread in one layer on a baking sheet and place them in the oven for about an hour. Turn the mushroom slices and blot off any excess moisture and continue to slow cook until all the moisture evaporates. Properly dried mushrooms can last for years. Rehydrate them as you would purchased dried porcini.