It partially comes down to sugar. By using more white granulated sugar it can lead to crispier cookies. That's because white sugar lets out a lot of water as it bakes, resulting in crispier cookies. You can also have crispier cookies if you bake them too long in the oven. Remember, cookies will continue to bake even after out of the oven. Chewy cookies are in part thanks to the equal parts sugar and egg yolks. An additional egg yolk will help obtained chewy cookies. That paired with cooking time. You will remove them out of the oven just as they begin to brown.