Beurre noisette is unsalted butter that has been lightly browned, though not burned. The term is French, literally meaning hazelnut (noisette) butter (beurre), though no hazelnuts are used in making this type of butter. In addition to changing color, beurre noisette takes on a nutty flavor not found in butter that has simply been melted. Hazelnut butter may be used in a variety of dishes including French pastries and as a topping to cooked vegetables to give them an added dimension of flavor.

Making beurre noisette is simple but it requires constant attention to prevent the butter from burning as burnt butter has a very bitter taste. Very browned butter, or beurre noir (black butter), is also used in French cuisine in a variety of dishes from eggs to vegetables.

Beurre noisette starts out as unsalted butter which is placed in a saucepan. Heavy-bottom saucepans are generally preferred, as thin pans usually expose the butter too quickly to the heat, causing the butter to be scorched. The butter is typically browned over medium heat — around 250°F degrees (about 121°C degrees). When the volume of butter in the pan has reduced by about one quarter, the heat is turned down low. Once light brown flecks appear, the pan is removed from the heat and set it in cool water to quickly reduce the heat.

Brown butter can be used in a variety of ways. When its used to flavor fish, poultry or vegetables, lemon juice is often added, usually in a one-to-four lemon juice-to-beurre noisette ratio. If the butter is used to sauté food, however, lemon usually isn't used. Beurre noisette is particularly popular for sautéing breaded food because it has a lower water content and therefore helps cerate a more crunchy exterior.

Buerre noisette is also frequently used in making French pastries, cakes and cookies. Madeleines and financiers — miniature cakes frequently found in French bakeries — often call for beurre noisette. Besides imparting a delicate nutty flavor, the browned butter gives pastries and cakes a toasty flavor.

Although beurre noisette can be made from traditional American-made butter, a number of chefs and culinary experts prefer making it from European or French butter. These butters, as well as hand churned speciality butters, frequently have more distinct flavors than American varieties.