Beurre noir or 'black butter', is a sauce made by cooking butter until it turns dark brown. A little vinegar or lemon juice is added to the butter, then flavorings such as capers or parsley. Beurre noir is best served with grilled or fried fish, eggs and vegetables dishes. Beurre noisette is similar to beurre noir, but the butter is cooked only until it is medium-brown, then the seasonings are added.
** Asian Online Recipes