Top-ranked recipe named "Sauce Bearnaise In An Electric Blender"
Boil the Vinegar, Wine. Shallots, and the seasonings over moderate heat until the liquid has reduced to 2 tablespoons. Let it cool and then strain it.
Place the egg yolks, and strained juice in the blender jar. Cover the jar and blend the egg yolk mixture at top speed for 2 seconds. Uncover, and still blending at top speed, immediately start pouring on the hot butter in a thin stream of droplets.