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.
The sauce was likely first created by the chef Collinet, the inventor of puffed potatoes (pommes de terre soufflées), and served at the 1836 opening of Le Pavillon Henri IV, a restaurant at Saint-Germain-en-Laye, not far from Paris. Evidence for this is reinforced by the fact that the restaurant was named for Henry IV of France, a gourmet himself, who was born in the former province of Béarn.
A Béarnaise sauce is simply an egg yolk, a shallot, a little tarragon vinegar. It takes years of practice for the result to be perfect.
Like Hollandaise sauce, there are several methods for the preparation of Béarnaise sauce. Please refer to the Preparation section of that article for basics. Here we highlight the differences.
The most common preparation is a bain marie method where a reduction of vinegar is used to acidify the yolks. Escoffier calls for a reduction of wine, vinegar, shallots, fresh chervil, fresh tarragon and crushed peppercorns (later strained out), with fresh tarragon and chervil to finish instead of lemon juice. Others are similar. Alternatively, the flavorings may be added to a finished Hollandaise (sans lemon juice).
Adding Tarragon does not make a Faux Bearnaise.