These cheeses are defined more by the way they are made than by the milk used. There are soft-paste cheeses that are left unpressed precisely so that the penicillium mold, which is what defines and characterizes them, can develop naturally in the gaps in the curds. The cheeses are first brushed with the mould then left in a cool, very damp atmosphere so that the mold can gradually penetrate, forming the characteristic blue veins.
All Spanish blue cheese comes from the same geographical area in the Picos de Europa mountain range in north-central Spain or, more specifically in the triangle formed by the provinces of León, Asturias and Cantabria, a natural paradise for cheese-making. The many natural caves in which the cheese is stored while ripening offer ideal conditions for spontaneous generation of the mold. Some of these cheeses, such as the famous Cabrales, are the Spanish contribution to the top-ranking blue cheeses, standing alongside Roquefort, Gorgonzola and Stilton.