If you have cookies on your holiday baking list this year, knowing a little about each ingredient and the role they play in your batter or dough can help you control the crispness/chewiness/melt-in-your-mouth texture of your cookies.
Butter: Butter is the best choice for baking because of its great flavour - it also has a low melting point, so your cookies will spread better. Make sure it’s at room temperature, or it will be impossible to beat - rather than risk melting it in the microwave, grate it on the coarse side of a box grater to soften it quickly and evenly for baking. Salted is fine for baking, even if a recipe calls for unsalted - you need some salt in your cookies anyway.
White (granulated) sugar: doughs high in white (granulated) sugar tend to produce crisper cookies - as the cookies cool, the sugar crystallizes and the cookies harden. They also tend to turn a deeper golden.
Brown sugar: is moister and makes for a more chewy cookie - it's also hygroscopic (absorbs moisture from the atmosphere) so cookies made with brown sugar are chewier and often become softer as they cool, rather than crisper. To make your own, add 1 Tbsp. molasses to 1 cup sugar - the more molasses you add, the browner the sugar.
Eggs: recipes assume you will use large eggs. They help bind the dough together, but also add a cakey texture – any wet ingredients, in fact, will produce a more cakey cookie. Eggs also act as a leavening agent, so add another if you want to add more lift.
Flour: all-purpose flour is great for cookie baking - just make sure you don't add too much of it. Stir it around in its container or bag to aerate it a bit before scooping it out and leveling it off with a knife.
Baking: if you want a chewy cookie, make sure you don't overbake them - they should be golden around the edges, but still soft in the middle. Keep in mind they'll firm up as they cool.