If you need to substitute chocolate for brownies, you can try using cocoa powder in place of the melted chocolate. Cocoa powder is produced from ground cocoa beans and has a deep chocolate flavor. For each ounce (28 grams) of melted semisweet or bittersweet baking chocolate called for in your recipe, use 3 tablespoons of cocoa powder plus 1 tablespoon of butter, shortening or oil to make up for the lost fat in the melted chocolate. If your recipe calls for unsweetened baking chocolate, substitute an equal amount of cocoa powder plus 4-6 teaspoons of sugar for each ounce (28 grams). You can also use dark or semi-sweet chopped bars instead, but you may need to adjust the cooking time as needed.