Olive Oil
Mushrooms are an important ingredient in Italian cooking and porcini mushrooms are highly prized for their heady, woodsy flavor. Fresh porcini are available just a few weeks out of the year (you would use them like you would any other fresh mushroom), but luckily dried porcini are available year round and can be found at nearly any supermarket.
The drying process not only extends the shelf life of the porcini, but it also intensifies its flavor. Using just a small amount of dried porcini can add an incredibly deep, rich mushroom flavor. When using dried porcini, it is important to first rinse them of any dirt or sand. For recipes with longer cooking times, you can simply mince the dried porcini and add them to the pot near the beginning of the cooking time. For recipes with shorter cooking times, however, it is best to soften and rehydrate the dried porcini in warm water before chopping them and stirring them into the pot along with rehydrating liquid (which should be strained of grit).
When buying porcini mushrooms, look for mushrooms that are large and thick and either tan or brown. Avoid packages with lots of dust and crumbled bits, and keep an eye out for small pinholes, telltale signs that worms got to the mushrooms. Eyeballing is good, but smelling the mushrooms is also helpful to judge quality. Purchase dried porcini with an earthy (not musty or stale) aroma; mushrooms with no aroma at all are likely to have little or no flavor.