Typically cookies turn out puffy if they have more flour than the recipe calls for. It's best to measure flour with a kitchen scale, as you can get wildly different amounts of flour by using a cup measure, depending on how you fill the cup. If you are using a cup measure instead of a scale, first fluff the flour in its bag, then use a spoon to place it into your measuring cup. Level the flour off by scraping the flat edge of a knife across the top of the cup measure