About Béarnaise sauce
Béarnaise sauce (French: Sauce béarnaise) [be.aʁnɛz] is a sauce made of clarified butter emulsified in egg yolks and flavored with herbs. It is considered to be a 'child' of the mother Hollandaise sauce, one of the five sauces in the French haute cuisine mother sauce repertoire. The difference is only in their flavoring: Béarnaise uses shallot, chervil, peppercorn, and tarragon while Hollandaise uses lemon juice.
Béarnaise is a traditional sauce for steak.