Homemade cookies that are too hard or that start out soft and then become hard after only a couple of days can be disappointing to a soft-cookie lover. A part of how your cookies come out has to do with the individual recipe that you use. Other reasons for having hard cookies come out of the oven when you expect soft cookies include ingredient types, temperatures, and inconsistent measuring.
Low-fat and no-fat ingredients can have up to 20% more water content in them. This causes excess spreading of the dough as the cookie bakes, creating a flatter, crispier cookie. Do not replace full-fat ingredients with low-fat ones unless the recipe is modified specifically for a low-fat recipe.
Measure wet and dry ingredients consistently. Flour should be stirred to fluff and loosen it before spooning it gently into a measuring cup. Once filled, the flour should be scraped flat without packing it down. Soft cookies need moisture retained; too much flour can produce overly dry and crispy cookies. Brown sugar should always be tightly packed, and unless a recipe calls for refrigerated butter, it should always be room temperature.
Use larger scoops of dough for each cookie. A larger scoop means a fluffier cookie which makes it easier to avoid overcooking the center.
Time it by the cookie, not the clock. A soft cookie should be lightly golden brown with a lighter center. Sunset.com recommends that about 1/3 of the cookie's center should still be pale.
Keep finished cookies soft. Once your cookies have completely cooled pack them in an airtight container and place a slice or two of white bread on top of them. The sugar in the cookies will absorb the moisture in the bread, helping the cookies stay moist and chewy. Bread should be removed and replaced with fresh bread every other day to keep the bread from molding.