Béarnaise sauce (; french: [be.aʁ.nɛz]) is a sauce made of butter, egg yolk, white-wine vinegar, and herbs. it is regarded as a "child" of hollandaise sauce. the difference is only in the flavoring: béarnaise uses shallot, black pepper, and tarragon, while hollandaise uses white pepper or a pinch of cayenne. the sauce's name derives from the province of béarn, france. it is a traditional sauce for steak.
Source: Wikipedia