Slice the white parts of the leeks then soak the leek slices in cold water for a few minutes. Swish the leek around to separate the pieces and to make sure the leek is clean. Drain well. In a saucepan, heat one tablespoon of olive oil and the butter and saute the leek and garlic until the pieces are soft and slightly golden around the edges. Add the grated potato and chicken or vegetable stock and bring to the boil. Simmer for 15 minutes until the potato is tender. Add the rocket and simmer for 1 minute. Puree the soup using a wand or in a blender until smooth. Transfer the soup to a cold metal mixing bowl and place the bowl in a sink full of cold water. This will chill the soup as quickly as possible to avoid the rocket loosing its fresh green colour. Fold in the sour cream or yoghurt and season to taste with salt and pepper. Preheat the oven to 220?c. Remove the crusts from the bread and slice the bread into small cubes. Heat the oil in small frypan and add the chopped rosemary. When the rosemary is fragrant, pour the oil over the bread cubes and toss thoroughly. Transfer the bread cubes to a baking tray and bake the bread cubes for 10 minutes or until golden brown. Remove from the oven and cool. To serve, ladle the soup into bowls and top with an extra dollop of sour cream or yoghurt. Add some finely diced tomato and croutons and chives before serving. Per serving: 705 Calories (kcal); 40g Total Fat; (49% calories from fat); 10g Protein; 83g Carbohydrate; 31mg Cholesterol; 191mg Sodium Food Exchanges: 3 Grain(Starch); 0 Lean Meat; 7 1/2 Vegetable; 0 Fruit; 7 1/2 Fat; 0 Other Carbohydrates Converted by MM_Buster v2.0n.