For greater umami, just add kelp

WHENEVER I SEE THE leathery black kelp known in Japan as kombu, I think of my mother, reaching into our pantry and retrieving a sheet or two several times each day. As a little girl in Tokyo, I had no idea why kombu was so important to her cooking; I just knew it was omnipresent. As I grew older, I learned that infusing this kelp in water makes an elemental stock with a round, rich taste, a mild sweetness and a touch of saltiness from the sea—the basis for countless Japanese dishes, and the source of their profound depth of flavor.
Umami, the savory "fifth taste" that gives foods like anchovies and shiitake mushrooms their meaty depth, is found in kombu in a greater concentration than in any other food. Derived naturally from the amino acid glutamate, umami has an unusual capacity to draw out and highlight the flavors of other ingredients. To make the basic Japanese kelp stock—one of the easiest ways to bring it to your cooking—simply soak the kombu leaf in water overnight.

Long used in soups, braised dishes, dressings and sauces in Japan, umami-rich kelp stock has recently begun to play a key role in the kitchens of Western chefs seeking cleaner, leaner preparations that are nevertheless full of flavor. I've lived in New York for 14 years now, and during that time I've developed dozens of recipes for American-style fare that gets a savory boost from the kelp stock I grew up with. It's a kind of magic ingredient that builds flavor even as it saves time and effort.

For instance, in the recipe for sake-braised short ribs at right, I use kelp stock in place of mirepoix, the classic French flavor base of aromatic vegetables sautéed in oil. This substitution not only makes the recipe quicker and simpler to prepare, it also produces more flavorful meat and a lighter dish overall. Kelp stock also enhances the earthy sweetness of my creamy turnip soup garnished with zesty mustard and shaved fennel. And in my chorizo-and-shrimp rice, a dish inspired by my travels in Spain, kelp stock magnifies the umami impact of the sausage and shellfish and the briny character of the clam juice that the rice simmers in.

Kombu is available at most Asian markets as well as some of the larger American supermarkets, such as Whole Foods. Look for leaves that are thoroughly dried and firm to the touch. The color should be deep black-green with a touch of glossiness and no brown blemishes. You should also see a very faint white layer of mannite, a natural powder that is a carbohydrate and source of sweetness. Once the package has been opened, it will keep for about a year if wrapped tightly, secured with a rubber band and stored in a cool, dry cabinet. You can also purchase finely shredded kombu, available online at sources such as theingredientfinder.com. This form of kombu releases even more umami flavor into the stock, and it is compact and easy to store, as well.

On a properly cold day, I like to prepare a traditional Japanese wintertime dish that is one of the best ways I know to appreciate kombu. Called yudofu, or hot water tofu, it is something my mother often cooked for us, the simplest of hot pots. To make it, just simmer a block of soft tofu gently in water along with one or two large pieces of kombu until everything is heated through; to eat it, pluck pieces of tofu from the pot and dip them into a soy-based sauce. In my childhood home, once the tofu had been eaten, it was the custom to cut up the succulent kelp and eat it, too. I still do this in my own home, savoring the flavor of the kombu—salty, sweet, round and rich—with every bite.