This simple recipe transforms leafy greens into a silky-textured, vibrant puree. The soup's rich color makes this dish a natural choice for a spring brunch -- or a lush first course for an intimate dinner.
In a large heavy pot or Dutch oven, heat oil over medium-low heat. Add onion and garlic; cover and cook, stirring occasionally until onion has softened, about 3 minutes. Add potato and broth, and raise heat to high; bring the mixture to a boil.
Reduce heat to medium; cover and simmer until potato is tender, about 10 minutes. Stir in the parsley and cook, uncovered, until parsley is wilted, about 2 minutes.
Working in batches, puree mixture in blender until smooth; season with salt and pepper. Ladle into individual soup bowls and garnish, if desired, with one of the optional garnishes. Serve immediately.
You can keep leftovers in the refrigerator for several days; reheat them over a low flame to preserve the color.