Can unsweetened cocoa powder be used instead of unsweetened or semisweet chocolate squares or chips?

"Can unsweetened cocoa powder be used instead of unsweetened or semisweet chocolate squares or chips? If so, how do you determine measurements?"

To replace one ounce of unsweetened chocolate, use 3 tablespoons cocoa powder plus 1 tablespoon butter, shortening or oil. Dissolve the cocoa in liquid that is already used in the recipe.

To replace one ounce of semisweet chocolate, use 3 tablespoons of cocoa plus only 1 1/2 teaspoons of butter, shortening or oil and 1 to 1 1/2 tablespoons of sugar.

For more information on different types of chocolate, see All About Chocolate and, from Cooking Light, Chocolate Essentials.