How to Make Cookies Chewy
To make cookies chewy, try adding a tablespoon of honey or molasses to the dough before you bake the cookies. You can also replace the white sugar in the recipe with brown sugar since brown sugar contains more moisture. Also, try replacing the egg whites with egg yolks so you have 2 yolks for every 1 egg that the recipe calls for.
Add molasses or honey to your cookies. Adding a tablespoon of molasses (21g) to your cookie dough will increase the cookies' moisture content, giving them a soft, chewy texture. If you're not fond of molasses' deep flavor, try a tablespoon of honey. Don't add multiple tablespoons of liquid sweetener like the ones listed because they will make your cookies runny and too sweet. One tablespoon is enough to make your cookies softer but not disrupt the integrity of the dough. Substitute brown sugar for white sugar. Brown sugar is more moist than white sugar, so using it gives a chewier result. Replace the white sugar in your recipe 1-1 with brown sugar. This will also give your cookies a deeper, more caramelized flavor. Use recipes that call for shortening instead of butter. Butter contains fat, milk solids and water, whereas shortening is 100% pure fat. Using butter in cookies (due to the water) actually creates steam during the baking process, drying your cookies slightly. Shortening will create a chewier, more tender result. If you want to replace butter with shortening in a recipe, do so with a 1-1 ratio. Substitute an egg yolk for an egg white. This means that for each egg a recipe calls for, you would use two yolks instead. Yolks have more fat than egg whites, increasing the fat content of your cookies and keeping them moist. Opt for recipes with baking powder over baking soda. Baking powder is more acidic than baking soda, which means your cookies will spread less. This will prevent excess moisture loss as the cookie thins. Turn down the temperature on your oven. Many cookie recipes call for an oven temperature of 350 degrees F (176 degrees C) or higher. These hot temperatures cause your cookies to lose lots of moisture—and chewiness—in the baking process. Seek out recipes that call for an oven of around 325 degrees F (162 degrees C) to keep your cookies moist. Bake your cookies for less time. If you have a cookie recipe you like but the cookies turn out crunchy, try baking the cookies for slightly less time. If you take your cookies out when the exterior edges are golden brown but the centers are set but not brown, the cookies will be fudgier. Rest your dough in the fridge before baking. Chilling your dough in the fridge for at least an hour makes some water evaporate from your cookies, giving your dough a higher sugar content. This slightly higher sugar content will keep your cookies moist and chewy. The longer you rest your dough, the chewier the cookies. Professional bakers often rest their dough for several days to get the desired chewy texture. Don't go longer than a week in the fridge though. Allow cookies to cool completely, but don’t leave them out. Before storing your cookies, allow them to cool completely on the baking sheet. Then, store them promptly once they reach room temperature. Leaving them out will encourage them to dry out. Store cookies in an airtight container. To keep your cookies their most chewy and moist, store them in an airtight container such as a cookie jar with a lid or a Tupperware. If you don't have either of those, a Ziplock bag will do just fine. Make sure your cookies are not hot when you store them. Storing hot cookies in an airtight container will cause the cookies to fall apart. Add a slice of fresh bread to your storage container. To keep your cookies chewy and moist longer, add a slice of fresh sandwich bread to your storage container with the cookies. This will add moisture to the container, which the cookies will absorb. You'll know the method is working because the next day your slice of bread will be dried out like a piece of toast, and your cookies will be soft and chewy. 
Add molasses or honey to your cookies. Substitute brown sugar for white sugar. Use recipes that call for shortening instead of butter. Substitute an egg yolk for an egg white. Opt for recipes with baking powder over baking soda. Turn down the temperature on your oven. Bake your cookies for less time. Rest your dough in the fridge before baking. Allow cookies to cool completely, but don’t leave them out. Store cookies in an airtight container. Add a slice of fresh bread to your storage container. 