Method
Prep:20min  ›  Cook:25min  ›  Ready in:45min 

1. Heat the oil in a saucepan, add the leeks and garlic, and cook for 10 minutes, stirring frequently, until the leeks are slightly softened but not coloured. Pour in the stock and bring to the boil. Cover the pan, reduce the heat and simmer for 10 minutes or until the leeks are cooked.
2. Remove the soup from the heat and let it cool slightly, then purée it in a blender or food processor. Alternatively the soup can be puréed in the saucepan with a hand-held blender. Pour the soup into a bowl and leave it to cool, then chill well.
3. Just before serving the soup, prepare the avocado. Halve the avocado and discard the stone. Scoop the flesh from the peel and press through a fine stainless-steel or nylon sieve. The avocado can also be puréed in a blender or food processor until smooth, adding a little of the chilled soup to thin the purée and ensure it is completely smooth.
4. Stir the avocado purée into the soup together with the yogurt, lime juice and coriander. Add seasoning to taste, then ladle the soup into 4 bowls. Float 2–3 ice cubes in each bowl, if you wish, then add slices of lime and sprigs of coriander. Serve at once.

Some more ideas

This soup is also good hot. Purée the hot soup with the avocado and stir in half-fat crème fraîche instead of yogurt. * For a soup with Mexican flavours, cook 1–2 seeded and finely chopped fresh green chillies with the leeks. * For a simple no-cook avocado soup, blend 2 avocados with 450 ml (15 fl oz) vegetable stock, then add the yogurt and lime juice, and season to taste. * To make vichyssoise, the chilled leek and potato soup, use 1 litre (1¾ pints) stock and cook 2 peeled, sliced potatoes with the leeks. Omit the avocado, coriander and lime juice. * Serve sprinkled with snipped fresh chives.

Plus points

Half an avocado provides a quarter of the recommended daily intake of vitamin B6 and useful amounts of vitamin E and potassium. Although avocados are high in fat, they contain the healthier, mono-unsaturated type. * Leeks provide useful amounts of folate, which is important for proper blood cell formation and development of the nervous system in an unborn baby.

Each serving provides

Good source of potassium, vitamin B6, vitamin C, vitamin E. Useful source of folate, vitamin A, vitamin B1.