For chicken consomme' the broth must be absolutely fat-free and clear. Put the previously made Double Chicken Broth (see other recipe) back into an 4 quart pan and boil slowly until it has reduced to one half or one third its original volume. To remove any lingering traces of fat, strain into a 2-1/2 quart pan through a sieve lined with cheesecloth or a linen towel. To clarify the stock, add 1 egg white, beaten to a froth, and 1 crushed eggshell. Over medium heat, beat well with a rotary beater or a wire whisk until the stock comes to a boil and the egg white rises to the surface (it will have gathered together any impurities in the soup that would cloud it). Stop stirring, remove pan from the heat, and let it stand for 5 minutes, to settle. Then, without agitating the stock, strain it through a sieve or colander lined with several thicknesses of damp cheesecloth, or a linen towel that you have wrung out in cold water. This traps the impurities in the egg white and any vestige of fat that might remain is chilled by the damp cloth. The liquid should just drip through into the bowl beneath it. Don't attempt to hurry the process or you won't get a perfectly clear consomme'. When it has all dripped through, pour into plastic containers, cool, and then freeze.