Chilled Yogurt and Cucumber Soup

Cucumbers should be small and firm, with underdeveloped seeds. Peel thinly and cut into very small dice. Place in a large bowl. Add yogurt, spring onions, mint and olive oil and stir well. Add iced water until soup is a thin cream consistency - amount depends on thickness of the yogurt. Season to taste with salt and pepper. Set bowl in another bowl of ice for serving, and float cucumber slices and mint sprigs on top.