From America's Test Kitchen Season 10: The Cookie Jar
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.
Makes 16 cookies
Avoid using a nonstick skillet to brown the butter; the dark color of the nonstick coating makes it difficult to gauge when the butter is browned. Use fresh, moist brown sugar instead of hardened brown sugar, which will make the cookies dry. This recipe works with light brown sugar, but the cookies will be less full-flavored. For our winning brand of chocolate chips, see related tasting.