Definition from Wiktionary, the free dictionary
porcini (plural porcini)
- An edible mushroom (Boletus edulis), prized for its flavor.
- Robbie, on the other hand, on his first trip out with Clara's brother Licio, gathered twenty-three porcini (more than his guide) 
Although derived from the Italian plural, this noun is used for both singular and plural.
mushroom, Boletus edulis
- plural form of