To Thicken Sauces

When this is done with the yolks of eggs, they should first be well beaten, and then mixed with a spoonful of cold stock should it be at hand, and with one or two of the boiling sauce, which should be stirred very quickly to them, and they must in turn be stirred briskly to the sauce, which may be held over the fire, and well shaken for an instant afterwards, but never placed upon it, nor allowed to boil.

To the roux or French thickening (which follows), the gravy or other liquid which is to be mixed with it should be poured boiling and in small quantities, the saucepan being often well shaken round, and the sauce made to boil up after each portion is added. If this precaution be observed, the butter will never float upon the surface, but the whole will be well and smoothly blended: it will otherwise be difficult to clear the sauce from it perfectly.