Friday, December 4, 2015
Cookie Science; Written by Bravetart
Have you ever made strawberry shortcake and thought to yourself, "Why do I whip the cream, and what happens if I don't?" Probably not. The difference between a dollop and a drizzle of cream is so obvious, no one thinks to question the necessity of it. Yet the value of creaming, a closely related process, is harder to grasp. See, unlike stirring, mixing, or beating, creaming isn't about combining ingredients—it's about aerating them. By bashing butter against the sides of a bowl, whether you're going at it with a spatula or with a stand mixer, you're folding it over and over, creating little pockets of air with every turn. Add sugar, and suddenly that process is way more effective, building up an expansive network of sugar crystals, fat, and air. In pastry-speak, this process is described as "mechanical leavening": physically cramming air into a dough so that it'll puff up in the oven like a hot-air balloon. Google around, and that's what you'll be told, time and again. Creaming adds air. Air is fluffy. Fluffy is good. Good is great. Yay, cookies! While some recipes may only ask you to cream the butter and sugar until well combined, most invoke the phrase "light and fluffy." Both techniques have merit (the former intentionally cultivating a denser dough), but here I'm gonna stick to addressing the mysteries of "light and fluffy" alone. Butter doesn't begin to melt until it reaches about 90°F, but its ability to stretch and expand during the creaming process tops out at a mere 68°F. Anything above that, and you're flirting with disaster. If your butter is creeping above 70°F, you might as well not cream at all—the warm butter won't retain any air, leading to a dense dough and collapsed cookies. The common explanation of that process suggests the benefits of creaming only kick after you pop those cookies into the oven and they puff up. Until then, all that air's just waiting around for some heat to get it going, right? Wrong. Before you even start scooping the dough, something's already happened. Something miraculous. Something no one ever tells you: Creaming just added five to ten extra cookies to the batch. The actual number of bonus cookies will vary with each recipe, but the phenomenon is very real. I start by creaming the butter and sugar together for five minutes, until everything is light and fluffy, then add an egg and beat it for a minute longer. After five minutes of creaming, the mixture will warm to about 67°F. A cold egg added at this point isn't simply convenient; it's strategic, ensuring that the butter never tops 68°F. Given the typical ratio of ingredients and the sheer power of an electric mixer, it's virtually impossible for a single large egg to break a cookie dough, so fear not. Peek into the mixing bowl, and it'll be hard to tell just how drastically I've altered my dough. Air is almost impossible to visualize, even when you're looking at it. Watching butter and sugar as they're creamed together is about as dramatic as sorting through shades of beige at Sherwin-Williams. "Snow White" sugar and "Daffodil" butter lighten to "Antique Ivory," then "Elegant Ecru," shifting colors so subtly that some part of you screams, "It's all the same!" But it's really, really not. When you first mix butter and sugar together, they have the heavy and dense texture of wet sand. After a minute of creaming at medium speed, the paste begins to feel more like clay—damp and compact, but still not very sticky. Another minute, and it begins to soften, clinging to whatever it touches. From there, the network of sugar and air continues to stretch and grow. When properly creamed, my sugar cookie dough can be divided into 26 two-tablespoon portions, weighing one ounce each. When the ingredients are simply mixed together without that creaming step, the number drops to 21, at a heavier 1.25 ounces each. And before you shrug, remember this: They're not bigger cookies, they're denser cookies. Those dense lumps behave very differently on a hot baking sheet in the oven. For starters, they conduct heat better, which means that the butter and sugar melt faster, spreading the cookies flatter and thinner. On top of that, the tightly packed dough traps the carbon dioxide produced by leavenings like baking soda and baking powder. With nowhere to go, those pockets of air don't just gently lift the cookies; they smash their way through them. Cream the butter and sugar properly, though, and the cookie dough will be loaded with micro pockets of air. That air is a poor conductor of heat, which means that it helps insulate the dough from the hot baking sheet in the oven, slowing the rate at which the butter and sugar melt. Meanwhile, those air pockets begin to swell with steam, a gentle upward draft that helps hold the dough aloft. When the cookie finally sets, the air's footprint forms its crumb. The extent to which you experience the effect of those air pockets depends on a comical number of variables. Did you use a hand mixer or a stand mixer? What was the horsepower? Did the butter come to room temperature? What is room temperature? Where do you live? Is the A/C on? How many lights are there? Ultimately, it's a game of averages. That's why so many recipes keep things vague with instructions like "room-temperature" butter or mixing until "light and fluffy" without any indication of time or temperature. By providing flexible parameters, recipes can guide you to your destination with a reasonable amount of success, while leaving you to sort out the details of your journey. Whatever your recipe, remember that creaming is a process, so it can produce a spectrum of results. You may never experience anything so dramatic as a cookie that goes splat and wrinkly or weird, but the more consistent your approach, the more consistent your finished product.