The American Family Cook Book (1963) provides this simple recipe for Cream of Watercress Soup. It takes very few ingredients to highlight the fresh, peppery flavor of watercress; with just a handful of ingredients, you have an easy recipe that makes a perfect starter or light meal on its own. The vibrant green of the watercress is balanced by a touch of salt and a rich base, resulting in a smooth, creamy texture and a delightful flavor profile. Serve it warm with a crusty slice of bread or a dollop of cream for added richness. A note: delicate watercress wilts quickly, so it's often sold with its roots intact to retain moisture. The roots must remain so until the watercress is used.
Wash watercress. Chop leaves fine, reserving 2 tablespoons for garnish. Put remaining watercress in a saucepan. Add salt and 2 cups of water. Simmer for 10 minutes. Add hot white sauce. Mix well. Serve, garnished with reserved watercress. Serves 4.