The Science of the Best Chocolate Chip Cookies
[Photographs: J. Kenji Lopez-Alt]
"Stop making cookies."
I’m sorry, what was that dear?
"I said, stop making cookies.”
That’s odd, I thought to myself. Why would she be saying that? Wouldn’t any wife be pleased to be married to a husband who fills the house with the aroma of warm butter, caramelized sugar, and gooey chocolate? Indeed, wouldn’t any human being in the right mind yearn to be constantly surrounded by sweet, crisp-and-chewy snacks?
Then, as I glanced around the apartment, wiping chocolate-specked hands against my apron, running a finger across the countertop and tracing a line into the dusting of white powder that coated every surface in the kitchen, eyeing the dozens of bags of failed experimental cookies that blocked the television, opening the refrigerator door to discover that more than half of its contents were batches of uncooked cookie dough in various stages of rest, I thought, maybe she does have a point.
For the past few months, I’ve had chocolate chip cookies on the brain. I wake up in the middle of the night with a fresh idea, a new test to run, only to discover that my 10 pound flour bin has been emptied for the third time. Did I really use it all up that fast? I’d put on my coat and walk out in the cold New York winter night, my sandals leaving tracks in the snow as I wander the neighborhood, an addict searching for a convenience store that will sell me flour at 3 in the morning.
You see, I’ve never been able to get a chocolate chip cookie exactly the way I like. I’m talking chocolate cookies that are barely crisp around the edges with a buttery, toffee-like crunch that transitions into a chewy, moist center that bends like caramel, rich with butter and big pockets of melted chocolate. Cookies with crackly, craggy tops and the complex aroma of butterscotch. And of course, that elusive perfect balance between sweet and salty.
Some have come close, but none have quite hit the mark. And the bigger problem? I was never sure what to change in order to get what I want. Cookies are fickle and the advice out there is conflicting. Does more sugar make for crisper cookies? What about brown versus white? Does it matter how I incorporate the chocolate chips or whether the flour is blended in or folded? How about the butter: cold, warm, or melted?
So many questions to ask and answers to explore! I made it my goal to test each and every element from ingredients to cooking process, leaving no chocolate chip unturned in my quest for the best. 32 pounds of flour, over 100 individual tests, and 1,536 cookies later, I had my answers.
How Cookies Crumble
Most traditional chocolate chip cookie recipes start with the same basic ingredients and technique: butter and sugar (a mix of white and brown) are creamed together with a touch of vanilla until fluffy, eggs are beaten in one at a time, followed by flour, salt, and some sort of chemical leavening (baking soda, baking powder, or a bit of both). The mixture is combined just until it comes together, then spooned onto a baking sheet and baked.
When you bake a cookie, here’s what’s going on, step-by-step.
- The dough spreads:. As the butter warms, it slackens. The cookie dough begins to turn more liquid and gradually spreads out.
- The edges set: As the cookie spreads, the edges thin out. This, coupled with the fact that they are fully exposed to the heat of the oven and are constantly reaching hotter areas of the baking pan, causes them to begin to set long before the center of the cookie does.
- The cookie rises: As the butter melts and the cookie’s structure loosens, this frees up water, which in turn dissolves baking soda. This baking soda is then able to react with the acidic components of brown sugar, creating gases that cause the cookies to rise up and develop a more open interior structure.
- Egg proteins and starches set: Once they get hot enough, egg proteins and hydrated starches will begin to set in structure, finalizing the shape and size of the finished cookie.
- Sugar caramelizes: At its hottest areas—the edges and the underbelly in direct contact with the baking dish—sugar granules melt together, turning liquidy before starting to caramelize and brown, producing rich, sweet flavors.
- The Maillard reaction occurs: Proteins in the flour and the eggs brown along with the sugar in a process called the Maillard reaction—the same reaction responsible for giving your hamburger or bread a brown crust. It produces nutty, savory, toasted flavors.
- The cookie cools. Once it comes out of the oven, the process isn’t over yet. Remember that liquefied sugar? Well as the cookie cools, that liquid sugar hardens up, which can give the cookie an extra-crisp, toffee-like texture around the edges. Meanwhile, the air inside cools, which causes the cookie to deflate slightly, though when fully baked, the structure lent by eggs and flour will help it retain some of its rise.