Casu Marzu is literally rotten/putrid cheese that contains live maggots that eat the cheese and defecate back into the cheese block forming a soft spread enjoyed by the citizens of Sardinian and food delicacy elites around the world.
Casu Marzu is made by introducing fly larvae to the cheese to cause an advanced level of fermentation. The fats in the cheese break down quickly and cause the cheese to become soft, almost liquid in some cases. The cheese becomes so full of ammonia that it can sting when you eat it and the aftertaste can last for hours. It has a pungent stench and hundreds of wriggling maggots.
The cheese has been banned by the EU but is still for sale in Sardinian with some risk of fines.