Making a chewy chocolate chip cookie is mostly about adding more activated gluten. So, if you want your cookies still chewier, make them with bread flour instead of the normal all-purpose. Increasing the proportion of brown sugar vis-à-vis white sugar will also add chew (plus an even deeper, richer flavor). Why? Well, molasses is gunky stuff, let’s not forget, full of cane stalk flotsam and jetsam that interferes with sugar molecules as they attempt to pile onto one another to form crystals. The result will be sugar structures that are more like caramel than they are hard candy.