Portobello mushrooms are brown crimini mushrooms with a big cap and a meaty texture. Once the crimini reaches 4 to 5 inches in diameter, it's labeled a portobello. Grill, roast or saute these specimens to stand in for meat in a burger or to serve as a side dish at your next meal. The portobellos' large size may make cleaning seem daunting, but you should treat them just like any other brown mushroom as they're simply a mature version of the Agaricus bisporus fungus from which their cultivated.
Picking the Perfect 'Shroom
Purchase portobellos that are heavy and plump. Skip any specimens with withered edges or dried-out stems; mushrooms with slimy gills should also be avoided. Once you get them home, wrap them lightly in a dry paper towel and refrigerate them for as long as six days. Alternatively, allow them to remain in an unsealed plastic bag in the refrigerator. Removing the gills before storage could extend their shelf life slightly.
A portobello, like any mushroom, acts like a sponge when introduced to water. A water-logged mushroom steams and fails to get a roasted, meaty flavor upon cooking. Use a soft brush, cheesecloth or a dry paper towel to gently wipe off the surface of the 'shroom. If you must rinse your mushrooms, do so quickly and lightly, and dry them thoroughly before cooking. A salad spinner can help you remove any excess moisture. Avoid submerging the gills in water as they become extremely soggy.
Trimming Off the Bits
If you plan to saute the mushrooms in pieces, you could simply trim off the stem -- if it's attached -- and slice before using. The black gills on a portobello are quite prominent, though, and they can turn your entire dish a dingy color. You may prefer to remove them along with the somewhat woody stem. Simply pull off the stem where it attaches to the cap and reserve them to make a mushroom broth for future dishes. Use the tip of a spoon to lightly scrape away the gills and reveal a white inner layer of mushroom. Discard the gills. If you're broiling or grilling the whole caps to use in a sandwich, for example, take these steps to remove the gills and stems.
Cleaning Baby 'Bellas and Pre-Sliced 'Shrooms
Baby bellas are a clever marketing name for crimini mushrooms. Treat them in much the same way as you do their mature portobello brothers, but you don't need to remove the stem and gills unless you plan to use them for stuffing. These mushrooms benefit from a dry brushing before cooking rather than a good bath; they can be sliced and used as a side dish, roasted whole or stuffed for an appetizer. Presliced portabellos present a unique cleaning problem, as the amount of exposed flesh in these versions will become particularly sodden if exposed to too much water. Rinse them quickly and dry thoroughly before cooking -- either in a salad spinner or by patting dry with paper towels. Be sure to clean the mushrooms just before you use them, or any water they are exposed to will speed their degradation.