Formaggio di Fossa is a cheese from Sogliano al Rubicone in the Emilia-Romagna region of Italy.The cheese's name, which literally means cheese of the pit , is derived from the process of ripening the cheese in special underground pits.ossa cheese is made with either sheep's milk, cow's milk, or a mixture of the two. The cheese typically matures around 30 days before being placed in the fossa, a pit dug into the ground and lined with straw. The pit is prepared by burning straw inside to remove moisture and sterilize the space.