Sorrel speaks of spring. Then and all summer long, it grows freely as a weed in most New England pastures and gardens. When picked young and fresh, it is ideal for cooking.
Wash the sorrel leaves and cook them in the butter until just wilted. Puree the sorrel and add other ingredients, dissolving the cornstarch first in a little stock, or whirl all together in the blender. Then cook the soup over gentle heat until slightly thickened. Serve hot or chilled, garnished with sour cream and chives, or with thin slices of lemon.