A dash of mystery and a smidge of longing — this is how my love affair with the Chocolate Espresso Chew began. We first met at Firehook Bakery in Washington, D.C., 10 years ago. It was instant lust. The cookie's crackly exterior hid an intensely fudgy inside. Was the confection's contrast of textures — somewhere between a meringue and a brownie — the secret to its magic? Or was it the espresso's jolt or the chocolate's intensity? Whatever the reason for its appeal, I found myself craving it, making excuses to be near the bakery at snack time which (let's be honest) was anytime between 10 a.m. and 5 p.m..

The secret tryst lasted for years, though I recently 'fessed up to Kate Jansen, the genius behind the chew. About a year ago, she helped open Willow restaurant in Arlington, Va., taking her recipe for the Chocolate Espresso Chew with her. Unlike Firehook, which still serves up the enormous six-inch cookie ($1.45), she morphed it into a half-size version more suited to Willow's elegant surroundings (think dark wood accents and deep red walls).

The restaurant's main menu has complex flavors such as a braised leek, bacon and smoked goat cheese flatbread made in an open clay oven, or an herb-crusted yellowfin tuna with wild mushroom agnolotti. But Jansen, the co-owner and pastry chef, keeps her creations simple.

"For dessert, people want down-home. They're more willing to take risks with the savory, but they want familiar for dessert," Jansen says. Her cookie plate, featuring an assortment of four cookies and a dish of homemade ice cream ($6), is a top seller.

I joined Jansen in the kitchen to discover the secrets of this jewel. We went back and forth trying to transform the original recipe — which yielded 59.4 pounds of dough — to something manageable in a home kitchen. It was a happy struggle that took many, many batches to translate. And we got it close but couldn't create an exact match.

Turns out the missing link is not in the recipe but rather in the equipment. If you are lucky enough to have a convection oven, you will come much closer to the real deal. A traditional oven yields a version just as delicious: It's thicker and more brownielike but still shares the seductive melding of coffee and chocolate in the original. The result is an intense cookie you just might fall in love with.

This recipe will yield about 2 1/2 dozen 3-inch cookies, but you can make this simple cookie any size you want. Store in an airtight container for 2 to 3 days. For long-term freezing, wrap the cookies individually in aluminum foil and place in resealable plastic food storage bags.

CHOCOLATE ESPRESSO CHEW