Grüne Sosse (German-style Green Sauce) | Saveur

Ingredients

• 2 cups packed parsley
• 1 1⁄2 cups packed watercress
• 1 cup finely chopped chives
• 1 cup packed sorrel
• 1⁄2 cup buttermilk
• 1⁄2 cup plain Greek yogurt
• 1⁄2 cup sour cream
• 1 1⁄2 tsp. walnut oil
• 1 hard-boiled egg yolk
• 2 tbsp. fresh lemon juice
• Kosher salt and freshly ground black pepper, to taste