Cool, creamy, and loaded with fresh flavor, this is just about the most perfect summer soup we could imagine. Plus, it’s a great no-cook recipe for when the heat of summer hits and you want to keep your kitchen cool. While a large blender helps here, you could certainly prepare the soup in two batches and stir them together at the end. Serve as a light lunch or appetizer with crusty bread—or for a more substantial meal, this chilled watercress-cucumber soup is a delicious partner to our Ultimate Grilled Tomato Sandwich. In order to get sour cream that “swirls” into the soup (instead of sinking to the bottom), you’ll need to thin it out with a bit of water. In a small bowl, simply whisk together a 2-to-1 ratio of sour cream and water, and you’ll be good to go.