Tie all the seasonings up securely in a small cheesecloth bag.
Put chicken, boiling beef, veal and marrow bones in a large kettle. Add 3½ quarts of water and let boil slowly, skimming occasionally.
Cut vegetables into medium-sized pieces. Add with salt to meat mixture. Simmer 3 hours. Let cool. Strain through a cheesecloth.
Discard the bag of seasonings, the vegetables and the bones. Reserve chicken and meat pieces for use at another time.
Put the strained stock in a crock and add the beaten egg whites. Mix well. Return the stock to the kettle, and while it is boiling slowly, beat it in a figure 8 until it comes to a full boil. Remove from heat and let stand 20 minutes without stirring.
Strain again through a double cheesecloth. Add the liqueur, which will make the aspic crystal-clear.
(If the aspic seems a little limp, add 2 or 3 tablespoons of plain gelatin softened in cold water and dissolved in some hot aspic.) Kept cold, this aspic will be usable for weeks.