I've always been crazy about fresh herbs—so crazy, in fact, that I used to raid the Cloisters gardens in Manhattan, stealing a sprig of oregano, rosemary, or thyme just to keep myself in supply.
Today I have no need for tactics like that. I'm lucky enough to have my own garden that's full of many of my favorites: thyme, savory, chives, purple sage, spearmint, lavender, and more. And for those herbs that I just can't get to thrive in my front yard, I have another convenient (and legitimate) source: the local supermarket. Nowadays, well-stocked groceries often carry herbs like tarragon and marjoram alongside favorites like basil and rosemary.
Such availability is a dream come true for me, but I've noticed that many people are intimidated by this abundance of choice. How many passionate cooks (professionals as well as amateurs) buy fresh herbs, use maybe a few sprigs, and then proceed to forget about the rest of the bunch until they're dried out, limp, or spoiled? Many, I know. Why do they let these wonderfully fragrant flavorings expire in the back of their refrigerators? Because they don't know how best to store and handle them, and perhaps because they're a little afraid of using them. What herbs go with what food? How do you use them other than as a sprinkle to decorate a dish? When and how should they be added during cooking?
Once you have the answers to those questions, which I'm about to give you, you'll find yourself reaching for that bundle of herbs more and more often, and throwing them out less and less.
Finding and buying fresh herbs
Supermarkets package fresh herbs in various ways: loose in small plastic boxes, fastened in bunches with rubber bands, or sometimes still growing in a pot. No matter the packaging, look for herbs with vibrant color and aroma (open up those boxes for a sniff), and avoid those that are limp or yellowing, have black spots, or don't smell totally fresh and appetizing. I like to buy field-grown basil, parsley, mint, cilantro, and dill when possible—as opposed to greenhouse grown—because they're so much more fragrant. You can recognize field-grown herbs by their larger, hardier stalks and leaves. Some chefs prefer the more tender greenhouse herbs because they make a lovely delicate garnish and because they're ready to use straight from the bag.
It's worth exploring other sources for herbs, too, such as Middle Eastern, Latin, and Asian markets, which often carry herbs of higher quality and at lower prices than the supermarket.
Fragile herbs need TLC
Hardy herbs like rosemary, marjoram, and sage will stay green and fragrant for a week or two, as long as they're refrigerated and don't get wet. But tender herbs, such as basil, dill, cilantro, tarragon, and chervil, need special attention so they don't blacken or freeze in the refrigerator.
To keep tender herbs at their best, remove any rubber bands or fasteners. Because the roots draw the moisture from the leaves, it's important to trim off the root ends and the lower parts of the stems to prevent the tops from wilting. If the roots are large and prominent, you can save them to flavor soups or stocks. (Southeast Asian cooks chop up cilantro roots along with the leaves, while Jewish cooks like to add parsley roots to chicken soup.)
To keep pesto bright and green, be sure your food processor blade is sharp so it cuts without crushing the ingredients (if not, bring it to a knife sharpener). Then add the ingredients in the proper order: fat first, herbs last. I start with the oil and then add the garlic and pine nuts, puréeing them completely. Finally, add the greens, processing them for as short a time as possible so they stay cool and maintain their color.
Try other herbs besides basil in pesto (an Italian word simply meaning paste). Make a Southwest pesto with cilantro, pumpkin seeds, garlic, and aged Monterey Jack or Asiago cheese and a little fresh green chile. In cold weather, I make a sage, parsley, and walnut pesto to stir into a bowl of hearty white bean soup.