Sauce béarnaise is sauce hollandaise perfumed with vinegar and shallots.
Peel a shallot and cut it very fine. Put it into a saucepan with two spoonfuls of vinegar. Put it on the gas. Boil it until the vinegar has evaporated considerably. Add a spoonful of cold water. Salt. Lift it off the heat. Add two egg yolks and continue, employing the technique I have described for sauce hollandaise; that is to say, using a bain marie. This sauce is a delicious accompaniment to a fried steak or any grill.