The original instructions called for using "beurre manié", but I use a standard roux instead. A "beurre manié2 is made by kneading equal amounts of butter and flour together. It is usually added to liquids to thicken them after they have cooked for some time, such as for thickening the liquid from a braise or stew. By mixing the flour with the butter, it is possible to add the flour to a liquid without it forming lumps. In this recipe, because the flour is being added early in the cooking process, I elected to make a roux instead.