Sauce verte

If you want a sharper more vinegary taste you can add ½–1 teaspoon Dijon mustard to the egg yolks in the beginning. A touch of mustard is fabulous in a sauce verte, or green mayonnaise, which is made by adding 2 tablespoons or so of chopped herbs – sorrel, tarragon, parsley, whatever – and, classically, a handful of spinach, blanched (dunked for a few seconds in boiling water), super-efficientl