If you sift your flour — which you can do by tapping it through a metal sieve, or by just whisking out the lumps in a pinch — you guarantee smooth flour going into the mix, which helps avoid overmixing. So that's the first tip here: Sift your flour.

What causes overmixing?

Dough can get aerated, which means too much air can be incorporated into mixtures. Mixing goods for an extended period of time can also result in extra gluten development; which means that overmixing will give you cakes, cookies, muffins, pancakes, and breads which are gummy or unpleasantly chewy.

How do you make cookies not overmix?

Unless you want extra-crispy cookies, avoid overmixing your dough. "Overmixing your dough will result in flatter, crispier cookies," Cowan said. If you overmix, you will end up aerating the dough (adding air) which causes the cookies to rise and then fall, leaving you with flat cookies.