A block of pecorino cheese is cut open and left outside to attract cheese flies, Piophila casei, that lay up to 500 eggs in it. The larvae of cheese flies then feast on the cheese, and their enzymes break down the fats in the Sardinian sheep’s milk cheese. The larvae excrement is a partially digested soft cheese, almost liquid. 

The maggot cheese (also known as casu modde, casu cundídu, and casu fràzigu) is eaten with the living larvae, so diners need to protect their eyes from the jumping larvae. Eating live maggots is risky as they can survive inside their new host and can bore through intestinal walls. The worm cheese has a pungent smell and it burns your tongue, and it leaves a strong aftertaste that lasts for hours. Casu Marzu is banned in the EU and carries a fine of €40 000 for both the seller and the buyer. The local Sardinian government has along with the local worm cheese producers tried to get an exemption from the laws since it’s been made the same way for over 25 years. 

Casu Marzu means “Rotten or putrid cheese” A similar worm cheese exists in Corsica, Casgiu Merzu, and in Egypt, there is a version called Mish. The Disgusting Food Museum director was lucky enough to get to try Mish in the summer of 2019. The maggots can jump up to 15 cm and can attach to your eyeballs when you try to eat them, causing retinal detachment. 

The worm cheese should only be eaten when the larvae are still alive, dead maggots are considered a sign the worm cheese has gone bad. Exceptions can be made if the cheese has been refrigerated since that can kill the maggots. Some choose to not eat the larvae in the worm cheese, placing the cheese in a sealed paper bag where the larvae are starved for oxygen, moving and jumping around in the bag trying to survive causing a popping sound. When the sound has stopped, the larvae are dead and can be removed before eating the creamy substance.

The smell has been described as highly pungent and eating it burns the tongue. Some say it tastes like a very ripe Gorgonzola with the blue mold replaced by living larvae, it has a very distinct ammonia tasted. The after-taste stays in the mouth for hours. 

Versions of Casu Marzu:

• Casgiu merzu in Corsica
• Bross ch’a marcia in Piedmont;
• Cacie’ Punt (“formaggio punto”) in Molise;
• Casu puntu in Salento (Apulia);
• Casu du quagghiu in Calabria;
• Gorgonzola coi grilli in Liguria;
• Frmag punt in Apulia;
• Furmai nis (“formaggio nisso”) in Emilia-Romagna;
• Marcetto or cace fraceche in Abruzzo;
• Mish in Egypt;
• Salterello in Friuli-Venezia Giulia.