And the reason why it's so important.

Even if you're not into general Christmas merriment, there's no way that even the Scrooge-iest Scrooge out there doesn't enjoy holiday food, and more specifically, Christmas cookies.

Setting out cookies for Santa and participating in cookie swaps are two of the sweetest occasions during the season, but there are plenty of times (think: gifts for teachers and neighbors) when you'll bake throughout the holidays.

This year your cookies will be the favorite at every event because you did this one thing. Sarah Epperson, one of our Test Kitchen pros, shared one of her best-kept cooking-making secrets with us: always chill the cookie dough.

I know—it's not an actual secret. There are recipes and directions that specifically say to chill the dough or use chilled dough. But you probably didn't think that step was very important to the final product. You may have even heard that refrigerated cookie dough is unnecessary. As I recently learned, chilling the dough is extremely important. And like most good things in life, we owe it all to science and butter.

That's right. The composition of your cookies will come out differently after refrigeration because of the butter that's in the dough.

"When your cookie dough is not refrigerated, the butter is at room temperature. Therefore the heat from the oven reacts with the butter quickly, making it spread thinner," says Epperson.

And while some people prefer a crunchy, thin cookie, there are arguably many more people on team soft, thick cookie.

"When your dough is refrigerated, the butter hardens. So when you bake them, they spread less and hold their shape better," adds Epperson. "Which means a better likelihood of a soft, chewy cookie in the center."

So chilling the dough before baking means fluffier cookies with better consistency. Plus, if you have a bowl of dough ready in the refrigerator, it's much easier to scoop while chilled than at room temperature. Epperson said that like many foods, cookie dough benefits from resting (in the refrigerator, specifically) to let the flavors infuse and basically marinate together. So not only is the cookie's consistency going to be more even, but the actual flavor will be better, too!