Beurre manié is a paste made from flour and butter which is used as a sauce thickener. As the name suggests, it comes from the French culinary tradition, although beurre manié can be used in food from other nations as well. Sauces and stews are both thickened with the assistance of beurre manié, which should not be confused with roux. The paste is usually made in small amounts at the time of use.
In French, beurre manié means “kneaded butter.” The paste is made by working usually equal parts of butter and flour together so that the butter completely encases each grain of flour. When the beurre manié is added to a sauce or stew, the butter melts, releasing the flour and promoting thickening. Using beurre manié will eliminate clumping, since the flour is not added in a solid mass.
Because beurre manié is not cooked before use, it can add an undesired raw, floury flavor. For this reason, the sauce or stew is always cooked after the addition of the beurre manié, to neutralize the flavor. It also tends to be used in small amounts, so that the flour does not become overwhelming in the dish it is used in. For cooks who are just starting to learn how to use beurre manié, it is better to err on the side of caution and use less, rather than more.
Many cooks are familiar with roux, another thickening compound made from butter and flour. The two thickeners are actually very different, because roux is cooked before it is used. Frequently, roux acts as the base of a sauce, rather than a later addition. Finally, because of the browning process which occurs while roux is made, roux is used more in brown and colored sauces. Not all roux is brown, however. Lightly cooked roux will be almost white, and it will lend little in terms of flavor to the sauce it is used in, although it will act as a thickener.
It can be useful to know how to make roux, however, since it is very easy and it will transform dishes in which it is used. To make roux, measure out one tablespoon of butter into a pan on medium heat. Allow the butter to melt completely before adding one tablespoon of flour, and whisk the two together thoroughly. As the flour is whisked in, the roux will start to bubble and turn brown. Next, cream or milk can be added. The roux will made the sauce thick, and it will lend a mild tan color. Roux can also be made with other fats, such as lard.