Cocoa powder can be used in place of chocolate or baking chocolate in many recipes. Baking chocolate is essentially cocoa and fat and is usually unsweetened; so, when using cocoa powder as a substitute, there's no need to add sugar. If a recipe calls for melted sweetened chocolate, simply add sugar to the cocoa powder.
Measure the cocoa powder, fat and sugar, if using. For every 1 ounce unsweetened chocolate called for, you'll need 3 tablespoons cocoa powder and 1 tablespoon softened butter, vegetable oil or shortening. For 1 cup sweetened chocolate chips, you'll need 6 tablespoons cocoa powder, 7 tablespoons granulated sugar and 1/4 cup softened butter, vegetable oil or shortening.
Mix the cocoa powder and fat, or cocoa powder, fat and sugar if your recipe calls for sweetened chocolate. Combine thoroughly until the mixture resembles melted chocolate.
Add the chocolate mixture to the recipe, just as you would if using melted chocolate.