Portobella also called portabello is actually a full grown brown crimini mushroom. Once the small brown crimini grows up to be about 4" - 6" in diameter it is deemed to be a portobella.
In the U.S., portabellas have become ta popular "vegetarian meat". Grilled whole, these mushrooms make perfect meaty vegetarian burgers. They can also be stuffed and baked, or grilled and sliced over salads.
Portabellas are an excellent source of riboflavin, plus a good source of potassium, selenium and niacin. Like other mushrooms, portabellas also contain a powerful phytonutrient called ergothioneine.