Chef notes
Chocolate chip cookies get their chewy, toffee-like texture from a mixture of white and brown sugars. The sugars dissolve as they are whipped with the eggs, which is the same technique that gives great brownies a satin, crackly finish (you get that with these cookies, too). Think of sugar less as a singular "flavor" and more of a seasoning or enhancer, like salt. A little sugar nudges butter and flour into bolder, more vibrant versions of themselves. It can soften the edges of bitter, acidic chocolates. Use too much, though, and it mutes and dulls other ingredients.
The butter is browned until nutty and fragrant. Toasting wheat and buckwheat flours coaxes out their natural, earthen sweetness. Both the dark chocolate and the creamy semisweet chocolate are chopped into boulder-like chunks. Buy the best single-origin, ethically sourced vanilla extract you can find for the cookie's characteristic caramel undertones.
Technique tips: You will have about 3 tablespoons of brown butter left over. Save it for another use. Cookie doughs rich in butter and sugar need at least 1 or 2 days (and up to 4 days) to "age" in the refrigerator, otherwise they spread too much and taste greasy. As any dough rests, it hydrates, meaning the flour soaks up the moisture from the butter and eggs. That translates into a superior cookie with crisp edges and tender insides.
