Parmigiano Reggiano is a cheese strictly regulated by its PDO (Protected Designation of Origin). PDO regulates the region where Parmigiano Reggiano may be made, as well as what ingredients may go into the cheese (cows milk, salt, and rennet only), what animals who produce the milk may eat, and the size and shape of the wheels. True Parmigiano Reggiano like this one is easy to identify by its stamped rind. Parmigiano Reggiano is made with raw cows milk and aged at least 24 months for intense, complex flavors. It is a hard, dry cheese and has a hard pale-golden rind and a straw-colored interior with a rich, sharp flavor. Other flavor notes include nutty, sweet, grassy, and fruity.