Quote Originally Posted by Eden View Post
Different fats - the chewy and thin ones use butter, but the chewy ones use melted butter, while thin use room temp butter, the fluffy use shortening.

different leavening - the chewy and thin ones use baking soda, fluffy baking powder (and cake flour rather than regular)

chewy and thin also use milk and eggs and fluffy no liquid or egg, chewy has an extra egg yolk
And didn't the chewy use a different flour too?