This series of "Cookie Hacks" gives an overview of some of the ways in which you can customize a recipe to make a cookie that is exactly to your liking. Crispy, chewy, dry, moist, soft or dense... it's all about knowing which levers to pull. Time to play mad scientist in the kitchen.
Part I: Flour and Alternatives
Part II: Eggs and Fats
Part III: Sugar
Part IV: Leavening
Part V: Dough Mixing and Aging
Part VI: "Add-in's" and Baking
Cookie Hacks - Part V
#7 - Mixing Techniques:"Your KitchenAid has 8 settings for a reason"
Entire books could be written on the techniques and science behind the deceptively simple act of combining ingredients. Consider this a highlights reel.
If you've done any baking, you've probably noticed that most recipes call for first combining all of the wet ingredients and then slowly incorporating the dry ingredients. In certain instances, a recipe may call for stirring ingredients until they are just barely combined. Others recipes require prolonged mixing at high speeds - acts which might seem tantamount to dough abuse. Suffice it to say there is (or should be) a method to the madness.
Why are dry ingredients added to wet ingredients?
Most recipes call for mixing dry ingredients into wet ingredients. Do a quick test of the reverse process, and the reasoning becomes painfully obvious. When wet ingredients are poured into dry, the dry ingredients quickly absorb the moisture at the point of contact. The dry ingredients may actually seize, forming a very dense mass that, oddly enough, may resist further liquid absorption. But if you slowly add the dry ingredients into the wet, the wet dough has sufficient time to both absorb and evenly incorporate the dry ingredients.
In baking, be it bread or cookie or cake, there's a concept of "hydrating with flour". Don't try to control the moisture content of a dough by adding more liquid; rather, use flour. If mid-mix you notice that a dough is already well formed, even before you have added all of the flour called for by the recipe, then you can stop. The recipe may be wrong. And you can always add more flour later. But once added, good luck trying to take it back out!
Cookie Hack: Keep control of dough moisture by adding dry ingredients into wet ingredients.
Why do some recipes call for brief mixing while others call for extended mixing?
Gluten (wait, that's your answer for everything!)
There are other reasons, but with cookies, those elastic bonds are the primary consideration. Long and aggressive mixing produces more and stronger gluten bonds. If you want a final product that is flaky and not chewy, a short mix is best.
Cookie Hack: Keep mixing times short unless you want chewier, more bread-like cookies.
And what about mixing speed?
With cookies, setting your electric mixer to a low or medium-low speed is appropriate in most situations. This setting is sufficient for combining ingredients without "over-working" a dough. Higher speeds may heat a dough and make it tough.
Exceptions arise in recipes where air is used as a leavening agent (in the extreme example of meringues, this is critical to the structure of the cookie). In these situations, higher speeds are useful for capturing air among the other ingredients, such as whipped egg whites or creamed butter & sugar.
When whipping egg whites, start mixing at a low speed and slowly increase the speed as the egg whites begin to stabilize and stiffen. If adding sugar, wait until the egg whites can form soft peaks - sugar makes it harder for the protein bonds to form if added too early (and even then, add sugar slowly).
Cookie Hack: Experiment with air as a leavening agent by whipping egg whites or creaming butter & sugar prior to incorporating dry ingredients - this can result in lighter, air-leavened cookies.
#8 - Dough Aging:"With age comes wisdom... and flavor"
The idea is simple, but the effect can be significant. By letting a dough rest overnight (or even up to 36 hours), all of the ingredients have an opportunity to truly combine.
The protein bonds continue to develop as the flour becomes fully hydrated. Sugars completely dissolve. Spices and other flavoring agents become more evenly distributed. All of these factors come together to make a better cookie.
It can also be easier to work with a refrigerator-rested dough. The dough will be firmer and easier to portion into individual cookies. A rested and chilled dough will also be better able to retain its shape when baked, reducing the "spread" of the cookie.