Using a blender instead of a food processor makes this refreshing soup especially velvety and light. To chill it quickly, set the bowl in a larger bowl of ice water for about 30 minutes, stirring the soup occasionally. Cold Soup Recipes
In a blender, puree the cucumbers, a handful at a time, until smooth. Add the watercress, 6 of the dill sprigs, the vinegar, 1 tablespoon of the oil and 1 teaspoon of salt and puree until smooth.
Transfer the soup to a bowl and stir in the yogurt. Refrigerate until chilled, about 2 hours. Season with salt and pepper and pour into bowls. Garnish with the radishes, scallions and the remaining 4 dill sprigs. Drizzle with a little olive oil and serve.
The soup can be refrigerated overnight. Garnish before serving.