Feta helps put the "big" and "fat" in Greek weddings. Now the European Commission has ruled that only Greek cheese can be called "feta." (Other countries have five years to comply or win an appeal.) In the meantime, here's a guide: Greek feta, typically made from sheep's milk, is the "standard everything else is measured by," says Steven Jenkins, author of "Cheese Primer." French sheep's-milk feta is "sweeter and more buttery," says Daphne Zepos, fromagere at New York's Artisanal. Denmark uses cow's milk, which has "less genuine flavor," Zepos warns. For American feta, stick to small brands made from goat's milk.