What ingredients when added to Hollandaise make the sauce Bearnaise?

Wine and tarragon are added to hollandaise to create the classic sauce Béarnaise. More precisely, traditional recipes use a reduction of wine or wine vinegar, shallots, pepper, and tarragon, which is then combined with the egg-yolk-and-butter emulsion.

Béarnaise is considered a derivative, or “child,” of hollandaise. Both sauces depend on egg yolks to emulsify butter, but hollandaise is usually brightened with lemon juice, while Béarnaise gets its distinctive herbal, lightly anise-like flavor from tarragon and its sharper character from the reduction.

The name refers to Béarn, a historic region of southwestern France, although the sauce is generally associated with a restaurant near Paris. It is most famously served with steak, where its richness and acidity complement grilled meat.

A common mix-up is treating tarragon alone as the complete distinction. Tarragon is the defining herb, but classic versions also include an acidic wine or vinegar reduction and often shallot and chervil.