We're utilizing a few techniques to ensure these cookies turn out chewy and soft, rather than crunchy or cakey. First, we're using melted butter, which produces a chewier cookie. Using more brown sugar than granulated sugar also adds a chewier texture. Cornstarch helps soften the proteins in the dough, resulting in a softer cookie. Resting the dough allows some of the water to evaporate, which results in a chewier cookie that spreads less in the oven. Using parchment paper helps cookies spread less and prevents the bottoms from getting too crispy, which can happen when using a greased baking sheet.