Adapted from Julia Child's Blender Hollandaise Sauce.
3 egg yolks
1 T red wine vinegar
1 T fresh lemon juice
1 T dry vermouth
1/4 t salt
1/2 t dried tarragon
1 T shallots, minced
4 ounces (1 stick) real butter
Blend everything except butter in a blender at top speed for about 2 seconds. Melt butter until foaming hot. Pour butter into blender while blending at top speed, in a thin stream.
The Johnson Family Cookbook