Here's How To Keep Cookies Soft
Nothing tastes just like a soft, fresh, ever-so-slightly chewy cookie straight out of the oven. Unless we're super greedy, though, most of those just-baked cookies are going to stick around for a few days before they all get eaten. As each day goes by, the sad news is that those cookies will probably just keep getting harder and harder. While there are several mistakes that almost everyone makes while baking cookies, it's actually pretty easy to prevent those delicious nubs from getting harder over time.
So what makes cookies lose their softness in the first place, and is there anything we can do to stop this (or at least slow down the process)? Well, to answer the first question, cookies get harder as they lose moisture, and this moisture begins evaporating as soon the cookies come out of the oven. As for the second question, luckily, there are a few tricks you can use to make sure your cookies not only start out moist, but are able to retain their moisture for a longer time.
How to bake cookies that stay soft
PureWow suggests adding two tablespoons of brown sugar or one tablespoon of corn syrup to your cookie recipe, though you may need to reduce the amount of white sugar accordingly. Both of these sweeteners will add extra moisture to your cookie, and corn syrup will also give it a nice crisp edge.
You should also scoop the cookie dough out in mounds instead of flattening them, as this will allow the cookie centers to stay softer. Finally, try to underbake the cookies just a tad. Their still-gooey centers will solidify as they cool outside the oven, and will retain their softness for longer than a cookie that's baked to perfection but almost immediately starts to harden.
How to store cookies so they'll keep soft
Cookies must be stored in an airtight container as soon as they're cool enough to be transferred off the baking sheet without falling apart. The longer they are exposed to the air, the more moisture they will lose.
Another helpful storage trick is to toss a piece of bread (plain white or wheat, no flavors) into the container. The bread slice will transfer its own moisture to the cookies, which will help to extend their softness window. Just don't make the mistake of using too much bread, since this can actually backfire on you and make your cookies mushy. Yuck! In cookies, as in Mama Bear's chair, there's such a thing as "too soft," but using only half a slice of bread should make sure your cookies stay "just right" instead.