In the département of the Lot, just east of Bordeaux in southwestern France, feudal castles and bastides loom high above strategic limestone cliffs, and lush green hills hide secret châteaux and prehistoric caves. Rivers flow gently through fertile valleys, connecting medieval market towns, hamlets, and farms. Like the neighboring region of the Dordogne, the Lot is famous for its foie gras, confit of goose and duck, black truffles, and other delicacies—and is fiercely loyal to traditional methods of food production. Roadside signs, some as modest as a weathered piece of wood nailed to a tree, turn this ancient countryside into a landscape filled with culinary opportunities—as though every family farm here had its own specialty. It was by following one of these humble signs that I was led to my first taste of exquisite handmade walnut oil, which has been produced in the region since the 11th century.
André Castagné, the proprietor of Huilerie Familiale du Lac de Diane, near the town of Martel, was busy feeding a fire with walnut shells and working a hydraulic press when I arrived at his small mill. The rich aroma of roasting walnuts filled the air. Warm and friendly, Castagné welcomed me, and then proceeded to carry on a lively conversation with me while he bounced back and forth between the three pieces of equipment that make up his entire operation—an ancient mill made of granite, which grinds walnut meat to a paste; a cast-iron basin in which Castagné roasts the paste over a wood-burning fire; and a hydraulic press layered with stacks of steel plates, which extracts the rich, golden oil.
Castagné bought his mill in 1985 and rebuilt it to its original form. Now, he presses oil daily through the winter (once dried, walnuts keep well, and each fall's harvest lasts all year) and also sells foie gras and pâté made from his own ducks, among other farm products. "How about a taste?" he asked, having already poured the oil onto little plates for sampling. The flavor of the roasted nuts was immediate, followed by a delicate hint of maple. As I purchased bottles of oil and loaded up with walnut liqueur, tins of foie gras, and duck rillettes, he reminded me that "Walnut oil has no cholesterol."
Walnut oil, probably first made in Greece in the fourth century b.c., has gone in and out of favor through the ages. It enjoyed great popularity in Paris during the 12th and 13th centuries, for instance, until poppy seed oil became more fashionable. The 15th-century French king René d'Anjou had an irrational fear of olives and their by-products; he preferred walnut oil, planting groves of the trees in Aix. But a century later, the physician to King Francis I deemed walnut oil "too hot and caustic". And the 16th-century French poet Pierre de Ronsard described it as "useless". Until at least the end of the 18th century, however, walnuts remained sustenance for the agrarian poor. (Walnut shells were used to make bread in times of famine; the meat has been used to make a milk.) Today, with demand for flavorful, unsaturated oils on the rise, walnut oil has resumed its place of prominence.
Walnut oil, which smells and tastes a bit like a more rustic version of vanilla, is rarely used for cooking—it has a low smoke point, which means that it burns easily— but is a seasoning and dressing oil par excellence, treasured for its intense aroma, bold, nutty flavor, and unmistakably earthy character. In the Lot and adjacent regions, walnut oil is commonly drizzled over grilled duck or foie gras, or used in salads or as an ingredient in walnut cake (see recipe). In earlier times, the oil was also used in lamps, as a painting and varnishing medium, as a home remedy prescribed for everything from bed-wetting to mental illness—and even to treat cases of indigestion in sheep.
Its uses can also be somewhat more refined. Jean-Georges Vongerichten, chef-owner of New York's Jean Georges, Jo Jo, and Vong restaurants, for example, uses it to finish a sauce for lamb. "The strong flavor of the walnut oil stands up to that of the meat," he says. In the fall, he also drizzles walnut oil over mashed potatoes and uses it in a vinaigrette for a dish of sweetbreads with warm potato salad. Chef Gray Kunz of Lespinasse, also in New York City, fondly remembers "a wonderful dish I had in Bordeaux of roast leg of lamb with white beans, served together on a platter with a sprinkling of walnut oil." In his kitchen, Kunz uses it very economically, to season salads and to accent a dish of foie gras with toasted brioche. "Because it is so strong," he says, "I have my cooks keep it in squeeze bottles so they never use more than a few drops at a time." I like to pour it sparingly over asparagus, artichokes, or haricots verts myself, letting the steam carry its haunting scent.