Pine nuts

What they are: The edible sweet and buttery seeds of pine trees. About 20 species of pines produce seeds large enough for harvesting, with slight differences in flavor and appearance among the species. In the Mediterranean, long, slim pine nuts come from the Italian stone or umbrella pine. Crunchier, squatter, and more teardrop-shaped nuts are harvested from the Korean pine and the Chilgoza pine of the Western Himalayas. Closer to home, the Colorado pine and single leaf pine provide most of the harvest. Seeds from the Korean pine -- mostly those harvested in northeast China -- cost less than European or North American nuts. The Chinese variety makes up the bulk of international trade.

How to cook them: Pine nuts are perhaps best known for their role in the basil pesto of Italy's Genoa. In this versatile sauce, the pine nuts (pignoli in Italian) are toasted and then pounded with garlic, basil, grated pecorino cheese, and olive oil to form a bright green, fragrant paste. The pesto is used as a pasta sauce but is also stirred into minestrone soup. The Catalan picada sauce, for which pine nuts (pinons in Spanish) are pounded to a paste with garlic, parsley, and olive oil, is added to long-simmered Spanish dishes for a fresh taste. In many cuisines, pine nuts are scattered on cakes or tarts and pressed into cookies. They can also be eaten out of hand -- raw or toasted.

Where to buy them: Because of their high fat content, pine nuts turn rancid quickly. Store in an airtight container in the refrigerator for up to two months; freeze for up to six months. Buy Mediterranean nuts ($25 per pound) or Chinese ($15 per pound) at Dairy Fresh Candies, 57 Salem St., Boston, 617-742-2639. Penny Frazier of Goods From the Woods in Licking, Mo., sells pine nuts harvested from Nevada and New Mexico (800-267-6680 or www.pinenut.com) -- JONATHAN LEVITT