Salted Breton butter, churned from cultured cream and shot through with crystals of coarse salt, is the ingredient that underwrites almost every dish in the region.
The habit is a tax accident. The gabelle, the French salt tax, exempted Brittany from the fifteenth century onwards, so salt stayed cheap in the region long after it became a luxury elsewhere, and Breton dairies went on salting butter for preservation when the rest of France moved to sweet butter. Demi-sel carries between 0.5 and 3 percent salt; anything more is beurre salé. The best is churned slowly from cream ripened with lactic cultures overnight, then finished with fleur de sel from the Guérande pans so the crystals stay whole. In Rennes it goes on bread at the table, into the caramel and into the pan for every galette.
