Clear Tarragon Sauce

To a pint of good stock made from veal and poultry, add a small bunch of tarragon, the white of an egg whipped with a very little water, and a tablespoonful of tarragon vinegar; continue whisking this over the fire until it boils, and then remove it to the side, there to remain boiling until the egg is thoroughly set hard, and the aspic is perfectly bright; then strain it through a napkin into a stewpan, and boil it down to the consistency of half glaze.

This sauce or essence is used for quenelles, and boiled fowls or chickens.