Cut some veal in equal pieces, put them in a saucepan with water, salt, pepper, carrots, onions and parsley. Bring to the boil and skim well several times. When cooked put aside.
Put in a saucepan a spoonful of flour, a piece of butter the size of half an egg; stir well over the fire, add about a pint of the water in which the veal has boiled and cook till reduced by a quarter. Then add the pieces of veal (not the vegetables).
Prepare in a basin a mixture of two yolks of eggs, a small piece of butter and half a spoonful of vinegar; mix well and add the other gravy little by little. Put it all back in the saucepan and cook for a few minutes, shaking it occasionally. Be careful that it does not reach the boiling point. You can, if you like, add a few small mushrooms.