paragraph: 863.  INGREDIENTS.--The remains of a boiled calf's head, 1-1/2 pint of the liquor in which the head was boiled, 1 blade of pounded mace, 1 onion minced, a bunch of savoury herbs, salt and white pepper to taste, thickening of butter and flour, the yolks of 2 eggs, 1 tablespoonful of lemon-juice, forcemeat balls.  _Mode_.--Remove all the bones from the head, and cut the meat into nice square pieces.  Put 1-1/2 pint of the liquor it was boiled in into a saucepan, with mace, onion, herbs, and seasoning in the above proportion; let this simmer gently for 3/4 hour, then strain it and put in the meat.  When quite hot through, thicken the gravy with a little butter rolled in flour, and, just before dishing the fricassee, put in the beaten yolks of eggs and lemon-juice; but be particular, after these two latter ingredients are added, that the sauce does not boil, or it will curdle.  Garnish with forcemeat balls and curled slices of broiled bacon.  To insure the sauce being smooth, it is a good plan to dish the meat first, and then to add the eggs to the gravy: when these are set, the sauce may be poured over the meat. 
answer: During the boiling