Perfect Chocolate Chip Cookies

"Rich and buttery, with their soft cores and crispy edges, chocolate chip cookies are the American cookie-jar standard. Since Nestlé first began printing the recipe for Toll House cookies on the back of chocolate chip bags in 1939, generations of bakers have packed them into lunches and taken them to potlucks. But after a few samples, we wondered if this was really the best that a chocolate chip cookie could be. We wanted to refine this recipe to create a moist and chewy chocolate chip cookie with crisp edges and deep notes of toffee and butterscotch to balance its sweetness—in short, a more sophisticated cookie than the standard bake sale offering. Melting a generous amount of butter before combining it with other ingredients gave us the chewy texture we wanted. Since we were melting butter, we browned a portion of it to add nutty flavor. Using a bit more brown sugar than white sugar enhanced chewiness, while a combination of one egg and one egg yolk gave us supremely moist cookies. For the crisp edges and deep toffee flavor, we allowed the sugar to dissolve and rest in the melted butter. We baked the cookies until golden brown and just set, but still soft in the center. The resulting cookies were crisp and chewy and gooey with chocolate, and boasted a complex medley of sweet, buttery, caramel, and toffee flavors...."