Béarnaise is one of the classic sauces from French cuisine and it is great with steak. The traditional way of preparing it au bain marie requires quite a bit of skill, as the sauces curdles easily. It also requires you to make clarified butter first. And even though you should make clarified butter to cook the steak anyway, using a slightly different technique you can make sauce béarnaise easily with minimal risk of curdling.

Last night’s dinner: a nice juicy steak cooked sous-vide and then seared quickly in very hot clarified butter, hand cut fries, sauce béarnaise, a green salad, and a nice glass of Saint-Émilion Grand Cru.

There are some variation on the recipe, but the basic idea of béarnaise is a hollandaise with tarragon. Some recipes also add parsley and chervil. Some recipes use tarragon vinegar, but instead you can just as easily use the stems of the…