What is Cocoa Powder?
Cocoa powder is an unsweetened powder produced by grinding cacao beans and pressing out the cocoa butter (fat). (To learn more about chocolate production, see this article that explains how chocolate is made from bean to bar.) The resulting cocoa powder is low in fat, but has an intense chocolate taste. It is most commonly used in baked goods, where it is mixed with sugar and other fats, like butter, margarine, or coconut oil.
What's the Different Between Alkalized and Natural Cocoa Powder?
Cocoa powder is commonly available in two varieties: natural cocoa powder, and alkalized, or "dutch-processed," cocoa powder. Dutch-processing cocoa powder involves treating the cocoa with an alkali to reduce the acidity (and thus, remove sour flavors). Dutch-processed cocoa often has a deeper or redder brown color, and a more palatable flavor, since some of the acidity has been removed.
For candy making, the types of cocoa powder can usually be used interchangeably, and you should use whichever cocoa you think tastes best. For baking, the type of cocoa can matter, since the acidity of the cocoa powder can react with whatever leavening agent the recipe calls for. If the recipe calls for baking soda, natural cocoa powder is preferred, since the acidity in the cocoa will react well with the baking soda. If the recipe calls for baking powder, then Dutch-processed cocoa powder can be used.
Can I Use Cocoa Powder As A Substitute For Chocolate?
If you have a recipe that calls for melted unsweetened chocolate, it's easy to use cocoa powder as a substitute! For every 1 oz of unsweetened chocolate called for in the recipe, replace it with 3 level tablespoons of unsweetened chocolate plus 1 tablespoon of fat (melted butter, margarine, or oil).
Substituting melted unsweetened chocolate for cocoa powder is a much harder task, and isn't recommended, as the percentage of fat and cocoa solids are difficult to replicate in a simple formula. If you want to try, Serious Eats provides this conversion recommendation:
Weight of Unsweetened Chocolate x 5/8 = amount of needed cocoa powder
Weight of Unsweetened Chocolate x 3/8 = amount of needed additional fat
In other words, if a recipe calls for for 200 grams of unsweetened chocolate, multiply that quantity by 5/8, which equals 125. To determine the amount of additional fat needed, multiply 200 times 3/8 to get 75. Therefore, the adjusted recipe would use 125 grams of cocoa powder and 75 grams of fat. Since most people don't have pure cocoa butter in the cupboards, your best alternative is shortening, which is low in moisture, bland like cocoa butter, and melts in a similar way.
When Do I Use Cocoa Powder in Candy Making?
Cocoa powder is most frequently used as a coating on chocolate truffles! For a full listing of truffle recipes, see here. It's also used in other candy recipes, like Cocoa Mints, Chocolate Marshmallows, and Tiramisu Truffle Squares.