Blue cheese is any cheese inoculated with Penicillium mold (most often Penicillium roqueforti) that grows into visible blue-green veins through the interior during aging, giving it a sharp, tangy, sometimes pungent flavor and a creamy, crumbly texture. The tradition traces back to Roquefort, France, where the mold was first cultivated in the natural caves of Combalou to make sheep's-milk Roquefort cheese; the same mold strain is now used for many other varieties.
Major blue cheese styles differ by milk and region: Roquefort (sheep's milk, France), Stilton (cow's milk, England), and Gorgonzola (cow's milk, Italy) are the best known, alongside American varieties from Wisconsin and other dairy regions.
Blue cheese pairs well with sweet or acidic ingredients that offset its intensity, such as honey, figs, pears, or balsamic vinegar. It shows up in salad dressings, dips, burger and steak toppings, and savory tarts and pasta dishes, and is served on its own as part of a cheese course alongside nuts, dried fruit, and crusty bread.