The pea is one of the major groups within the vast legume family. Peas can be divided into three general categories: whole pea pods eaten young and fresh, shelled peas eaten fresh, and shelled peas that are dried.
Peas eaten fresh as whole pods include the broad, flat snow peas that star in Chinese stir-fries as well as plumper, rounder, bright green sugar snap peas.
The most common variety for shelling is the English, or garden, pea. Baby peas, or petits pois, refer to tiny, sweet English peas, while so-called early, or June, peas are larger and have more starch. The smaller ones need barely any cooking and are wonderful stirred into risotto at the last minute with a little grated Parmigiano-Reggiano cheese. Most are harvested for freezing.
The final category of peas, those that are usually dried, include yellow and green split peas, chickpeas and black-eyed peas. These are better grouped with beans and lentils because of their similar flavors and uses. Black-eyed peas are sometimes available fresh in the summer. If you buy them still in the pod, you will need to shell them before using them.
Choose fresh peas with crisp, smooth, glossy, bright green pods. Avoid any that are wilted, dried, puffy or blemished. For the sweetest flavor, try to purchase them from a farmers' market.
Canned peas bear so little resemblance to fresh peas that it is better to go without if they are the only option. Frozen shelled peas, on the other hand, are decent substitutes, especially if they will be cooked with other ingredients. Look for those labeled "baby" or "petite" for smaller, more delicate peas. Snow peas are available frozen as well, but frozen snow peas turn fairly soft and flavorless once cooked.
Because their natural sugar begins converting to starch immediately after they are picked, peas should be prepared and eaten as soon as possible, preferably the day of purchase. Peas will stay crisp for 3 to 4 days if stored in a plastic bag in the refrigerator, but do not expect them to retain their characteristic sweetness after a day.
For whole pea pods, snap off the tips of the pods, pulling down the length of the pod to remove any tough strings as well. Although many modern hybrids have no strings or the peas are processed before reaching the store, it is best to check. Whether pods or shelled, peas are best if steamed or blanched very briefly to retain their crisp texture and vibrant color.
For English peas, shell them just before cooking to prevent them from drying out. Work over a large bowl. After checking for and removing any strings as described above, squeeze the pod and press your thumb against the seam to split it open. Continuing the same movement, sweep your thumb down along the inside of the pod to pop out the peas. Discard the pod. (If making soup, save a few to sweeten the simmering stock.) If needed, refrigerate the peas for up to 1 day. Cover with damp paper towels or cold water to keep them moist.
Adapted from Williams-Sonoma Kitchen Companion: The A to Z Guide to Everyday Cooking, Equipment and Ingredients (Time-Life Books, 2000)