Most mushroom stems are edible. The only exception to this is the stem from a shiitake mushroom because it is tough and hard to chew through even when cooked.
Many people use mushrooms in soups, in salads, on pizza and in other dishes. When using mushrooms, wipe off the dirt on the outside and the mushroom is ready to go. Mushrooms can be used whole or sliced and diced. When using the stem, it is best to cut the tip off the bottom because that part tends to become spongy and hard.
When preparing mushrooms, especially large mushrooms like portabellas, many people choose to remove the stems before cooking. This is easy to do — pop the stem out of the cap and the mushroom is ready to cook. On a shiitake mushroom, since the stems are inedible, they will need to be removed. To do this, pinch the stem firmly at the area where it meets the cap, then pull it off, leaving as much of the cap as possible. Although the stems of oyster mushrooms are edible, many people prefer to cut them off and save them for stock or throw them away. Just cut around the stem and the caps will fall off.