GRUNE SOSSE (German-style green sauce, about 2 cups)
2 cups packed parsley
1-1/2 cups packed watercress
1 cup finely chopped chives
1 cup packed sorrel (if you can’t find sorrel, substitute baby spinach)
1/3 cup buttermilk
1/3 cup Greek yogurt
1/3 cup sour cream
1-1/2 teaspoons walnut oil
1 hard-boiled egg yolk
2 tablespoons fresh lemon juice
kosher salt and freshly ground black pepper, to taste
1.Process parsley, watercress, chives, sorrel, buttermilk, yogurt, sour cream, oil, egg yolk and lemon juice in a food processor until smooth; season with salt and pepper.
NOTE: Serve with grilled bratwursts.
from Saveur Magazine