Quickly parboiling green vegetables, or “blanching” them, locks in nutrition, flavor, and especially bright color. The key to successful blanching is to bring the vegetables immediately up to a boil, cook them only enough to tenderize them, and to stop the cooking by plunging them immediately into ice-cold water, a step known as “shocking” the vegetables. Salt plays an important role in keeping green vegetables green, and it is recommended in both the blanching and shocking waters.

The most important strategy, though, is to put only small batches of vegetables into a large amount of rapidly boiling water, ensuring that the water never stops boiling as they are added. If too much is added at once, the water cools, and the vegetables will fade. One pound of green beans, for example, should be cooked in four small batches, in four quarts of boiling, salted water. Each batch (about a handful) should boil rapidly from the moment it's put in the pot, until it is removed and shocked in ice water. Remove each batch from the shock water before adding the next.