Tips for Success

While most herbs can be chopped a few hours ahead with no ill effect, some are best prepared just before use. Cilantro becomes soapy tasting if chopped in advance. Basil becomes slimy and blackens once chopped. A chopped scallion (not a true herb but often used like one) starts to release a noticeably slimy residue as it sits and, like cilantro, can develop a soapy flavor. It's best to use each of these three immediately after chopping.

Some recipes recommend tearing fresh herbs instead of chopping them. Both tearing and chopping herbs help to release their natural oils and accentuate their flavor. We made two versions each of black bean salad with cilantro and quick tomato sauce with basil (one batch with torn herbs, the other with chopped). In both cases, tasters slightly preferred the chopped herbs, which dispersed more evenly; otherwise, big torn herbs could taste “overwhelming.” The bottom line? For pervasive herb flavor, stick with chopped herbs.

We had 26 staff members measure out 1 cup of basil in a dry measuring cup and then weighed the leaves. Samples were all over the place—those measuring gingerly ended up with 10 grams of basil; those who aggressively packed in the basil ended up with 29 grams. The average was 18.7 grams, which made the most balanced batch of pesto. We found that the best way to consistently get that average weight of basil—and any other type of fresh herb—was to lay the leaves in the measuring cup and press down just slightly, ensuring that there are no large air pockets and filling the cup just to its brim. (Do not pack the leaves down firmly into the cup.)

There’s no getting around it: Pesto looks the best right after you make it. With time, it can oxidize into a drab army green. Here are two methods that keep pesto bright green. One way is to blanch basil for 30 seconds in boiling water and then shock it in ice water before drying it and proceeding with the recipe. Blanching deactivates the enzyme that causes browning when cut basil leaves interact with oxygen. The second method is to add a bit of lemon juice. Lemon juice contains antioxidants plus citric and ascorbic acids. Just add 4 teaspoons of lemon juice per 2 cups of packed basil.