Treat fresh herbs like a bouquet of flowers: stems down in a few inches of water. Keep the bouquet loosely tented with a plastic produce bag and store in the refrigerator. This treatment keeps herbs hydrated but not too wet. Many herbs, like parsley, mint, and cilantro, may last up to two weeks this way. Exception: Cut basil is happiest around 55°F, which is colder than room temperature but warmer than the fridge.
Test kitchen experience has taught us that if basil is purchased already refrigerated, it should stay that way. If cut fresh or bought unrefrigerated, keep the basil at room temperature unless it’s very hot out. Regardless, cut basil rarely keeps longer than a week.
When ready to use the herbs, hold them by their stems and vigorously swish them around in a bowl of cool water until they seem free of dirt. Shake the herbs over the sink and then spin dry or blot dry with paper towels. (Curly parsley can be squeezed partially dry before blotting with paper towels.) The drier the herbs, the better they’ll withstand chopping.
Use a sharp chef’s knife in a rock-chopping motion (the front part of the knife should be moving in a slight slicing motion as you chop). The idea is to cut through the herbs cleanly, rather than bashing and bruising them, which happens if you use a dull knife. Bruised herbs bleed a lot of their flavor out onto the cutting board, and their color dulls or blackens quickly.
Watch the related video Chopping and Slicing Fresh Herbs.
Tip: Don’t throw out the cilantro stems
When preparing cilantro for chopping, you don’t necessarily have to remove all of the stems. Cilantro stems are quite flavorful, so if they’re thin and tender-crisp (bite one to check), just chop them up along with the leaves.