Sauce Béarnaise
The science
Béarnaise is Hollandaise with a reduction swapped in for the acid: tarragon, chervil, shallot, peppercorns, and vinegar are simmered down to a concentrated, aromatic, acidic essence that both seasons the sauce and supplies its water/acid phase. Tarragon's anise-like aroma is the signature; the reduction's acidity performs the same emulsion-stabilizing role lemon plays in the parent. It is arguably the single most important Hollandaise derivative.
Flavor profile
Hollandaise built on a reduction of tarragon, chervil, shallot, and vinegar/white wine (in place of plain lemon), finished with more fresh tarragon and chervil.
Culinary uses
The definitive sauce for grilled steak — steak frites, entrecôte béarnaise — and grilled meats and fish generally.
Reference notes
Parent: Hollandaise. Herb: tarragon (shared with Châteaubriand). Children: Foyot, Choron. Dishes: steak frites.