The best-quality cocoas have relatively high amounts of fat and the deepest, richest flavors. Cocoa is mildly acidic. These cookies owe their chocolatey intensity to cocoa. Natural and Dutched both work well here. Nonalkalized or natural cocoa has long been the base for traditional American recipes.
Natural cocoa is medium ochre brown in color and very bitter on the tongue.
Small amounts of potassium carbonate are used to reduce acidity in the cocoa beans. Depending on the degree of alkalization, its color ranges from medium and deep reddish brown to charcoal brown, and finally towards black in some specialty products. Both home cooks and food professionals are divided on their cocoa preferences, and many admit to confusion. Scores of recipes that I've tried with both natural and Dutch-processed reveal that the cocoa with the best flavor depends on how you use it.