Beurre noisette (French pronunciation: [bœʁ nwazɛt], literally hazelnut butter, loosely brown butter) is frequently used in French pastry production. It can also be used as a warm sauce to accompany many foods, such as winter vegetables, pasta, fish, omelettes, and chicken.
Unsalted butter is melted over low heat and allowed to separate into butterfat and milk solids. The milk solids naturally sink to the bottom of the pan and, if left over gentle heat, will begin to brown. As the milk solids reach a toasty hazelnut color, the pan is removed from the heat. Beurre noisette may be used in its liquid state, or cooled to a solid form. It has a nutty flavour and is particularly included in the batters for madeleines and financiers.