Dried porcinis pack a big umami punch. They area earthy, woody, and delicious, and can deepen the flavor of many varieties of dishes. Dried porcinis, like other varieties of dried, wild mushrooms are foraged from wild habitats. It is up to you whether you want to wash them prior to rehydrating, but if you opt to do so, you could just soak them in a lightly salted water for about 10-20 minutes. Keep in mind that if you do this, the mushrooms will begin the rehydration process. This step is fully optional. Whether or not you have soaked your mushrooms in salt water to clean, you will likely need to continue by fully reconstituting your mushrooms. In total, this should take about 30 minutes. Simply submerge them in the liquid of your choice (stock, water, cream). Once reconstituted, you can cook with your dried procinis as you would their fresh counterpart. Sauté them in oil or butter, throw them in stews, roast them. The options are endless. Check out this post for guidance on cooking with dried mushrooms.