Dutch cocoa goes through a specific treatment that gives it its signature color and flavor. It also results in a smoother finish and decreases its acidity compared to natural cocoa. Most baked goods will use leaveners like baking soda or baking powder, which are more basic than acidic. Using natural cocoa powder, which is more acidic than Dutch, helps control how the final product turns out.
Depending on the various combinations of cocoa and leavener, your baked goods will have different rises and intensity in flavor. Dutch cocoa creates a denser product with a more mellow flavor. If a recipe calls for Dutch-processed cocoa, it will say it in the ingredients. Otherwise, always use natural cocoa powder. For Amaretti, we want natural cocoa!