From America's Test Kitchen Season 4: Cookie Jar Favorites
Too often, thin and crispy chocolate chip cookies are tough and lack flavor. They can be too brittle, too crumbly, too dense, or too greasy. We wanted chocolate chip cookies that were thin, almost like praline cookies, and packed a big crunch without either breaking teeth or shattering into a million pieces when eaten. And they had to have the simple, gratifying flavors of deeply caramelized sugar and rich butter. For cookies with a notable butterscotch flavor and sufficient crunch, we turned to a combination of light brown sugar and white sugar. Next we focused on the thickness of our cookies. When butter is creamed with sugar, air cells are created in the batter; these cells expand during baking, leading to cookies that rise—and cookies with height were not what we wanted. So we used melted butter and milk to create a batter that would spread (not rise) in the oven, resulting in cookies with the perfect thin crispiness. A bit of baking soda and corn syrup promoted maximum browning and caramelization, and vanilla and salt gave our cookies the best flavor.
Makes about 4 dozen 2-inch cookies
The dough, en masse or shaped into balls and wrapped well, can be refrigerated up to 2 days or frozen up to 1 month. Be sure to bring it to room temperature before baking.