True parmesan cheese comes only from a specific area, around Parma and Reggio Emilia, and must be aged for up to two years in humid conditions before it is ready. Milk from cows fed on grass or hay is curdled in copper containers and heated to carefully controlled temperatures before being pressed into cloth-lined moulds. The best quality cheese can cost £10 per kilogramme. Alternatives, such as pecorino, made from sheep's milk, or Grana Padana, which comes from cows around the Po Valley near Milan and which takes just 15 months to mature, do not carry parmesan's badge of authenticity, the EU's Protected Geographical Indication label, as they do not share its traditional production methods.