• Dice the cucumber, and finely chop the onion. Place the cucumber in a saucepan with the stock and onion. Bring to the boil, cover and simmer for about 20 minutes, or until the cucumber is tender. Cool, then blend in a liquidiser until smooth.
• Melt the butter or margarine in a saucepan, stir in the flour and cook for 1 minute. Gradually add the cucumber puree. Bring to the boil, stirring frequently, then reduce the heat and simmer for 2 minutes. Season to taste. Add the natural yogurt and leave to cool thoroughly.
• Garnish each serving with ice cubes, mint sprigs and cucumber slices.

Cook's Tip

• Before adding the yogurt, whisk a tablespoon of mint jelly into the hot soup until dissolved.