Sea urchin? Lardo? Kohlrabi? I asked a top chefs at some of the world's hottest restaurants what ingredient they are currently obsessed with. (Hint: sometimes it's not as exotic as you'd think.)

Harold Dieterle, Kin Shop and Perilla, New York City
The ingredient that I'm kind of freaking about right now is sawtooth herb, which is also called culantro. It's in the cilantro family and its all leaf, the stem is really thin. I'm doing it in stir fries and salads, anywhere you would use cilantro. Some people find cilantro too soapy—I don't personally, I love cilantro—but sawtooth herb is a lot cleaner.

Jose Andres, Jaleo, Zaytinya and Oyamel in Washington, D.C., The Bazaar by Jose Andres in Los Angeles
I'm working right now on oysters, but from a historical perspective. Recipes from 16th and 17th century Manhattan that disappeared for some reason. Like pickled oysters with allspice, black pepper and vinegar.

KF Seetoh, It's All About Taste, Singapore
I'm obsessed with rempah, it's the art of blending spices. A spice paste with stuff like garlic, shallots, lemongrass, ginger, dried chile, fermented shrimp paste, blended and stir fried it into a wonderful sauce.

Susan Feniger, Street and Border Grill, Los Angeles
Pandan. I love it savory, I love it sweet, I love what it does to a dish. We do it in kaya toast, but we've been playing with using it in desserts—we're working on a cookie dish that's got pandan in it and another solid custard that's got pandan in it.

Richard Blais, Flip Burger Boutique, Atlanta
I'm obsessed with the color black: Black pasta, black garlic. I grew up in New York City, maybe I'm trying to get back there. It just seems like such a serious color and it doesn't get used a lot in food other than squid ink, but I'm into the black thing right now. But whatever, the wind changes tomorrow and I'll be into something else.