Porcini MushroomsPorcini mushrooms are commonly used in European cooking. So they work well as a substitute for shiitake mushrooms for Italian and American recipes. They’re hardy and have an intense earthy/nutty flavor which is similar to shiitake.
Dried ShiitakeDried shiitake are one of the best substitutes for shiitake mushrooms because they’re essentially the same. They last much longer in storage than their fresh counterparts and you can essentially cook with them the same way.
White Button MushroomsWhite button mushrooms are the easiest kind of mushroom to buy in the store and are usually the cheapest. Since they’re similar in size to shiitake mushrooms you can substitute them out