Almost every baking recipe calls for some kind of fat to be added to retain the moisture, flavor and texture of the baked good. This can take the form of oil, shortening or butter. However, while oil and shortening are full fat, butter has a slight amount of water. These items are interchangeable, however the end result will be slightly different. Butter adds a creamier flavor to any recipe and, in a pinch, can easily be used instead of shortening.
Chill the butter before use so that it retains a solid nature, similar to shortening, when baked.
Read the recipe to figure out how much shortening is called for.
Measure out the same amount of butter as the amount of shortening that is called for. The ratio is one part butter to one part shortening -- 1 cup of butter is equivalent to 1 cup of shortening.
If the butter is salted, remove 1/2 tsp. of salt from the recipe for every 1 cup of butter used. For example, if 1/2 cup salted butter is substituted for 1/2 cup shortening, remove 1/4 tsp. salt from the recipe.
If the recipe does not turn out as moist as you wanted it, add another 1/8 cup of butter in addition to the one to one ratio when baking. For example, use 1 1/8 cup of butter for every 1 cup of shortening called for.