There was a time when the wealthy had greenhouses and could grow plants. Therefore, they could make delicacies any time of the year. The tarragon and Chervil were always available. I can get chervil at the Farmer's Market only when the weather cooperates. I ran a netsearch on Béarnaise Sauce and the citations returned are all a monotone. Martha Stewart's is the same as Epicurious', as Ina