Brownies and chocolate cakes often call for unsweetened chocolate, which has to be melted carefully before being incorporated into a recipe. If you are worried about scorching the chocolate or don't want to buy an ingredient that you might not use again, you can substitute unsweetened cocoa powder for the baking chocolate. You will also have to add shortening or oil. Be sure to use only unsweetened cocoa, not a cocoa mix, and a flavorless oil such as canola oil.
Use 3 level tablespoons of unsweetened cocoa powder and one tablespoon of butter or shortening for each ounce of unsweetened chocolate in the recipe.
Melt butter or shortening in a microwave in 10-second intervals, stirring in between each interval. You can also melt the butter or solid shortening on a stove, over low heat. This will take a few minutes, depending on how much shortening you need. Stir continuously if you melt it on the stove.
Stir the unsweetened cocoa powder into the melted butter or shortening until smooth.