The portobello mushroom is a fully-grown Crimino mushroom which is an un-blanched version of the white button mushroom, commonly found in supermarkets. Although blanching usually refers to par cooking, in the agricultural industry it refers to growing produce in the absences of light, not allowing it to produce any color.
Because it’s an older version of a mushroom, the cap is spread out the “gills” are fully exposed. This leads to the mushroom slightly drying out, which in turn concentrates its flavors and gives it a sought after meaty texture.
To properly prep, start by removing the stem. This can be done by simply holding the cap in one hand and the stem in the other; give the stem a firm twist and it will come right off. The stem is removed because it is quite fibrous; however, this does not mean it should be thrown out. It’s a great addition to stock and when diced or finely sliced, adds a nice element to long simmered soups and stews.
Next, remove the black gills on the underside of the mushroom cap by scraping with the edge of a spoon. The gills are generally removed because their dark color will leach into your dish and unlike the cap itself, has a very mushy and un-appealing texture.
An optional step, if you want to your portobello cap to lay flatter so you can slice more uniformly, is to remove the outer edge that once helped to hold onto its gills.
Once the outer rim is removed the portobello can be julienned and diced for sautés, ravioli fillings or accompaniments to pastas.
Although the above technique finishes with the slicing of the portobello cap, I usually prefer applications that allow me to keep the cap whole, which offers more drama and visual appeal. You’ll often find portobello caps whole, brushed with olive oil and grilled for portobello sandwiches.
One of my favorite dishes ever done with a whole portobello cap was by my good friend Brian Motola. He first stuffed the cap with a mixture of goat cheese and herbs. Next he coated the whole thing with flour, egg and panko breadcrumbs. He then fried it to a crispy golden brown, sliced it into wedges, and served it over a pool of spicy marinara and a drizzle of good olive oil. Simple and excellent.