The ingredients are the same, it’s the ratios that are different. There is a bit more butter in the bars — plus the butter in this recipe is melted, making a chewier, brownie-like texture. There is also a different ratio of sugars. There is more brown sugar and less granulated sugar in bars than in the cookies. And there is an extra egg yolk in the bars. These differences will create a more brownie-like version of chocolate chip cookies.