first published at Luckypeach.com, this piece covers the basics of cookies, and gives recipes for both soft sugar cookies, and rolled sugar cookies. With Christmas cookie season upon us, I thought this refresher might assist in your own holiday baking.
Around December, my thoughts turn to all things cookie. I’m not alone. Magazines dedicated to holiday cookies line grocery store checkout lanes, and invites to cookie swaps pour in. But though magazines might overwhelm with endless cookie variations, the truth is that every cookie shares the same core ingredients: flour, sugar, butter, and eggs.
You might add chocolate or nuts, but it’s the varying ratios of these four main ingredients—and how we mix them together—that define our cookies. An understanding of how these ingredients interact is the key to cookie success.
The Fat: Please use real butter
The fat in your cookie will come from one of three main sources: oil, shortening, or butter. Butter is by far the most flavorful of the fats, and the most utilized in cookie making. Don’t make the mistake of substituting it with a butter-flavored margarine or tub-o-spread. These concoctions are often much higher in water, which makes them perfect for spreading on toast, but terrible for baking cookies. For the sake of consistency, all the fat called for here is butter, and unless a recipe seems to hinge on the use of shortening or oil, I suggest you too adopt an all-butter-all-the-time philosophy in your own cookie making.
To understand how butter works in your cookies, imagine heating two tablespoons of butter in a frying pan. One is a cold square cut straight from a stick of butter; the other, a blob of soft butter spooned from a stick at room temperature. The cold pat of butter will melt only at the edges, keeping its shape as the heat from the stove warms it up. The soft blob, however, will melt quickly, and shift shape, drooping and spreading as it liquefies.
This is exactly how the fat in your cookies will behave when baked in the oven. Soft fat will spread, and hard fat will hold its shape. Eventually all fat melts into flat puddles if not for the other ingredients getting in the way, but the underlying structure of the fat will help define how a cookie spreads—or doesn’t—in the oven.
Sugar: Not just a sweet face
Most recipes call for white sugar, the sparking granules of white sucrose we’re all familiar with. Perhaps because of this familiarity, many cooks fiddle with the amount of sugar in recipes, decreasing it for health reasons, or because they want a less sweet treat.
But before you do this, we need to we need to talk about what sugar really does. First and foremost, sugar adds flavor. Beyond the obvious sweetness, it also plays a key role in how other flavors are perceived, heightening some and diminishing the perception of others. But flavor isn’t where sugar’s true power lies.
The most important thing sugar does in your cookie is bind to water. Sugar is hygroscopic, which means it attracts and retains water. And once the water submits to its fate and binds to the sugar, it is no longer available to any of the other ingredients in the cookie—in particular, the protein in the flour. With the correct ratio of sugar, only a portion of the water in the cookie is left to mix with the protein and form strong gluten chains. If you add too much sugar, there will be very little water left to help build the protein structure in your cookie, and it might crackle and fall apart. Remove sugar from your cookie, and there will be excess water and it will activate the gluten, creating stronger protein chains, and tough cookie.
What does sugar look like when it binds to a water molecule? It takes on liquid properties and becomes a clear syrup. You won’t see this when it’s mixed into cookie dough. However when the cookie bakes, the water evaporates and leaves behind sugar crystals on the surface of the cookie. This is what gives a cookie a crispy edge, or, if baked long enough, crispness all the way through.
Flour: The G word
There are countless kind of flours you can make cookies with, but for this piece we’ll discuss the properties of wheat flour. Grocery stores usually carry three types: bread flour, which is high in protein and creates the chew in bread; cake flour, which is low in protein and high in starch, which creates the tender crumb of a soft cake; and all-purpose flour, which is likely what you already have in your cupboards, and has a mid-range protein content appropriate for most baked goods. For most cookies, the protein content in all-purpose flour is correct, and unless specified differently, the recipe was likely tested with all-purpose flour.
The flour is the last ingredient added to a cookie, where it performs its first task: bringing the sludge of sugar, fat, and egg together into a dough. The starches absorb water and glue the fats and sugars together. As the flour sits with the dough, the two proteins in wheat flour, glutenin and gliadin will absorb water and combine forces to form gluten chains, adding a subtle web of proteins for strength.
When baked in the oven, the protein web created by the gluten stretches and traps the expanding air in the cookie. Without it, the air would simply bubble up and out of the cookie like the gasses in your soda, passing through the sugars, fats, and starches leaving us with a flat puck of a cookie. While we don’t expect our cookies to inflate like a loaf of bread, we do need some of that air to stay inside.
But to fully understand wheat flour, we can’t just think of it as webs of gluten. All purpose flour contains 10-12% protein, which means about 90 percent of flour is starch, which make up the bulk of the flour. These small granules also absorb water. When they do, they swell, over twice their size, and when heated about 160, they turn soft and supple, “gelatinizing”. These gelatinized starches are tender and give a cookie most of its body. Just like the sugar, the water occupied by the starch granules is not available to participate in gluten formation. The flours we buy from commercial sources, rather than local mills, are formulated to have a specific ratio of starch and gluten that favor the muffins, cookies, and other baked goods typically produced in the home.
Some cookies, particularly those that are designed to hold a clean edge when baked, require more flour to help hold all the ingredients in place—both when rolled, and when baked. This puts the cookie at risk of being too tough. Adding a small amount of cornstarch or potato starch helps add bulk to the cookie and keep it in place, while preventing too many gluten chains from making the cookie tough. Use additional starches with caution, as they are quite effective. Too much starch and there will be no water left for gluten formation, causing your cookie to fall apart.
Eggs: The jack-of-all-trades
While eggs are most often added to cookie recipes whole, the whites and yolks can be separated, and added individually to accentuate their unique properties. Egg yolks are mostly made of lipids with a small amount of protein and water. Lipids, are fat and act like it, adding flavor and color to a cookie. The small amount of protein in the yolks will coagulate in the presence of heat, helping hold the cookie together.
The protein in an egg yolk can’t compare to the protein in a egg white. An egg white is primarily made of water and albumen, a long-strand protein that unravels and interlocks in the presence of heat. In a cookie, this protein helps create the structure along with the gluten. But it comes bundled with a lot of water, which can make the dough it sticky and wet if too much is added. Once baked, the additional water turns into steam and becomes trapped by the extra protein, giving the cookie a cake-like texture.
Air: The secret ingredient
Air. It’s not on the ingredient list, and it’s rarely talked about. But air, or lack thereof, in a cookie is the key difference in many cookies. There are three ways to create air in a cookie: mechanically, chemically, and physically.
Mechanically. If you’ve ever had to “cream” the butter and sugar together in a recipe, this is what’s happenng. Each time the beater moves through the mixture, it drags the sharp sugar crystals through the butter, scraping air pockets into the fat. If you watch sugar and butter creaming, you will notice it getting paler in color, and fluffier in texture. In order to allow the sugar crystals to scrape these pockets into the fat, your butter needs to be soft—just below room temperature is best. (If you’re getting super scientific, it should be between 60 and 65 degrees.) If your butter is any softer, the air pockets will collapse under the pressure of the beater as soon as you create them. An added bonus: dough with a high ratio of mechanically added air will also be soft, ready to scoop when cold, and eager to change shape in the oven.
Chemically. We can add air to a cookie by using a leavening agent, specifically baking soda or baking powder. We have all experimented with combining baking soda and vinegar in elementary school, watching it foam up and expand. That’s what is happening inside our cookie. The baking soda releases carbon dioxide when it comes in contact with water and acid. You might not think a sugar cookie is acidic, and you’re not mistaken. But the flour and sugar are acidic enough to activate the baking soda. Baking powder is made of baking soda mixed with an additional acid that doesn’t become soluble until it reaches temperatures above 140 F.. This means that as the cookie bakes and increases in temperature, it gets an additional boost of air right about the time the starches and protiens in the cookie are firming up.
Physically. As the oven temperature increases it turns the water in the butter (18% water by weight) and the eggs into steam. This steam is the powerful engine that inflates both puff pastry and pate de choux, and in a cookie will help inflate the air pockets already created by mechanical leavening.
To apply this information to easy-to-see (and easier-to-eat) results, see the following recipes for sugar cookies. They share the four core ingredients, but little else. The first is a soft, chewy cookie that spreads from a mound into a round disk, crispy on the exterior, soft and chewy on the interior. The second is a crisp, crunchy rolled sugar cookie cookie that holds its shape in the oven. Both will serve you well under various sprinkles and icings, and will find a happy home at any holiday table.