Casu in fiixi is a fresh curd cheese that gets its name from the name of the leaves of the fern that are used in the production, the setifera fern (Polystichum setiferum). It is still produced in Barbagia di Suelo, in Suelo, and to a lesser degree in Esterzili in central Sardinia. While not still sold, today it is produced on farms and in homes exclusively for home consumption. It is often given as a gift. The raw milk from animals at the end of lactation is curdled with goat or sheep rennet (today also industrially acquired rennet is used) with milk at milking temperature. While this takes place, the setifera fern is prepared. These leaves must be free of plant diseases and pests. They are washed and left to dry. A form made of steel or aluminum replaces the traditional wild pear wood forms, and is covered with a linen cloth. Above this is placed a base of fern leaves. Once the curds are ready, they are collected with a slotted spoon and placed onto this base, without any separation of the whey, only the rising of the cream to the top. Onto the curd is placed a layer of ferns, and this operation is repeated until the form is filled. The top is closed with a further layer of ferns and the edges of the cloth are pulled tight to allow for the whey to drain. The result is a milky white cheese with a thin rind of a few millimeters and a diameter between 15 and 20 cm. Imprints of the fern leaves are left as a sort of fossil in the paste of the cheese. The fern is tough and waterproof is almost tasteless in the cheese but serves to create the layers. About two hours after being made, it can be consumed up to 36 hours later, before it starts to acidify. Today, this time can be lengthened by refrigerated storage. Casu in filixi has a light milky taste with notes of grass from the pasture and from the contact with the ferns. Historically, Sardinian shepherds, mostly of sheep but also of goats and cows, moved into the plains only during the hard winders, following the tradition of transhumance. The cheese produced then was mainly fiore sardo. With the residual production of milk they made various types of fresh cheese, among which, with the last residual production between June and July, was casu in filixi. The cheese has been made in the area since at least the early 1900s. It is difficult to know how much casu in filixi is still made, as it is limited to home production. While there are attempts to raise awareness about this cheese, it is at risk of being lost due the fact that it is difficult to make a commercially sold product given the presence of the setifera fern that, despite the fact that it is waterproof and does not become part of the cheese paste, is still considered toxic.
The traditional products, local breeds, and know-how collected by the Ark of Taste belong to the communities that have preserved them over time. They have been shared and described here thanks to the efforts of the network that that Slow Food has developed around the world, with the objective of preserving them and raising awareness. The text from these descriptions may be used, without modifications and citing the source, for non-commercial purposes in line with the Slow Food philosophy.