To Make Roux.
A roux is a mixture of butter and flour cooked. It is generally added, uncooked, to thicken a sauce or a soup; but the flavor is much better if it is first cooked, and the sauce or soup is added to it. Professional French cooks always manage it in this way. When the butter is first brought to the boiling-point, in a small stew-pan or cup, the sifted flour is sprinkled in, and both are mixed well together over the fire with an egg-whisk, until the flour is well cooked; a part of the sauce or soup is then stirred in until it becomes smooth and thin enough to add to the main sauce or soup. If the roux is intended for a white sauce, it is not allowed to color; if for a brown sauce, it may color a little, or browned flour may be used.