Cocoa powder is the star ingredient in all sorts of chocolate recipes, from brownies and Bundt cakes to birthday cakes and cookies. It also blends well to make buttercream, can be mixed into ice cream, and is a delicious addition to any fudge recipe. While in many cases you can use natural and Dutch-process cocoa interchangeably, this is not so with baking. In some cases, the acidity of natural cocoa powder may be needed to activate the leavening agent in the dish.  Meanwhile, recipes that call for baking powder tend to also include Dutch-process cocoa rather than the natural kind. If your recipe requires Dutch-process cocoa powder and you only have the natural variety, you can still use it in an equivalent amount. But you will also need to add 1/8 teaspoon of either lemon juice, white vinegar, or cream of tartar for every 3 tablespoons of cocoa powder. If, however, your recipe calls for natural cocoa powder and you want to use Dutch-process, then you will need to add 1/8 teaspoon baking soda for every 3 tablespoons of cocoa powder in order to raise the acidity to the right level. Finally, if you are looking to create a rich chocolate sauce with cocoa powder, use the black variety. It gives a wonderfully deep color that no other cocoa powder can match.