Frankfurter Grüne Soße: Seven-Herb Sauce

4 packed cups (5 ounces) mixed fresh herbs: parsley, chives, chervil, cress (or alfalfa), pimpinelle (salad burnet), sorrel, borage, tarragon, and lemon balm 1⁄4 cup vegetable oil 4 hard-boiled eggs 1 cup plain yogurt 3 tablespoons white wine vinegar 1 tablespoon Dijon mustard Salt and freshly milled black pepper 1. Pick over the herbs for culls and remove the stems. Wash in cold water and dry very thoroughly. In addition to drying the herbs in a salad spinner, I wrap them in a clean dishtowel and pat gently. 2. Chop the herbs briefly in the blender with the oil, but do not overprocess. Peel the eggs and carefully separate the egg yolks from the whites. Add the egg yolks to the herbs and process the mixture very briefly in the blender. 3. Transfer the herbs to a bowl and stir in the yogurt, vinegar, and mustard. Chop the egg whites very finely and incorporate them into the sauce. Season with salt and pepper. Let the sauce stand for 30 minutes before serving. Chill if not serving right away. Stir the sauce before serving with boiled beef. The sauce is best eaten within a day. Makes 6 servings © 2013, Spoonfuls of Germany by Nadia Hassani