Roux

Roux’s are very effective and heat-stable thickeners. A roux is made by cooking a mixture of 50% (by weight) of flour and 50% fat.  Bleached flour, pastry and cake flours, with their lower protein/higher starch content, gives sauces and soups a satiny finish. Butter, whole or clarified are commonly used in making a roux.  Chicken fat, the fat from beef dripping or lard add additional flavor to a roux. Vegetable oils and shortening may be used when no additional flavor is desired.

There are generally three color variations on a roux, white, blond, and brown. These are also referred as light, medium and dark. Some cooks define other shades in-between these including a very dark, almost black roux.

A white roux has the aroma of freshly-baked bread and is used in a white sauce.  A blond roux has the aroma of freshly popped popcorn, a toasted flavor and is used to thicken sauces that are golden in color. A brown roux has deep nutty flavor and is used to thicken dark and richly flavored sauces and soups.

How long a roux is cooked determines its thickening power and flavor.  The longer a roux is cooked the darker the roux becomes. A dark roux has more flavor but significantly less thickening ability than a light roux.  For example, a dark roux used in a traditional gumbo recipe is more about the nutty flavor and color from the dark roux than its (limited) thickening ability.  For a roux to achieve its full thickening potential, the roux and liquid must be brought to a boil.  Liquids, especially those thickened with a lightly cooked white or blond roux should be simmered to cook out any raw flour taste.

When making a roux, use a heavy non-reactive pan and a wooden spoon or heat-proof spatula. Whisking a roux in a pan, especially an aluminum pan will turn the roux gray. When adding a roux to a liquid to thicken, the roux and liquid should be significantly different temperatures. Add a hot roux to cold liquid or a cold roux to hot liquid (Cold can refer room-temperature as well.) As a rule-of-thumb, one pound of a light roux will thicken one gallon of liquid to a medium-thick consistency of a cream soup or gravy.

Beurre Manié is an uncooked roux.  It is made by kneading equal amounts of softened butter and pastry or cake flour.  The small bit of the paste is then whisked into a hot liquid to achieve desire thickness.  A beurre mania is often used to thicken a small amount of sauce or a pan sauce.  Larger amounts of sauce would typically be thickened with a roux.  Like a roux, a liquid thickened with a beurre manié must reach the boiling point to achieve  its full thickening potential and should be simmered 3 to 5 minutes to remove any raw flout taste.