In my research, I chanced upon Baking Library's Homemade Subway Chocolate Chip Cookies. To me, baking is a form of Science; measurements have to be accurate and the type of ingredients used determine the taste of the baked goods. For instance, butter imparts a fragrance and flavour whereas unflavoured oils give a moist texture. Some of the technicalities of creating a chewy cookie texture have been succinctly and clearly explained by Bakertan.
<update> Refer to Soft baked Chewy Chocolate Chips Cookies Recipe for a variation!
<update> Refer to Soft baked Chewy Chocolate Chips Cookies Recipe for a variation!