Watercress is a star performer in so many ways.
I love the fat, green leaves in salads, sprinkled with rock salt in sandwiches, in a sauce and perhaps most of all in this soup, which is always a joy to make and eat.
This recipe is from Delia's Complete How to Cook. Serves 6-8
First of all melt the butter in a large thick-based saucepan, then add the prepared leeks, potato and watercress and stir them around so that they're coated with the melted butter.
Next sprinkle in some salt then cover with a lid and let the vegetables sweat over a very gentle heat for about 20 minutes, giving the mixture a good stir about halfway through. After that, add the stock, bring everything up to simmering point and simmer, covered, for about 10-15 minutes or until the vegetables are quite tender.
Then remove the pan from the heat and when it's cooled a little liquidise the soup – you'll need to do this in batches. Then return it all to the saucepan, swirl in three tablespoons of crème fraîche, season to taste and reheat very gently. Serve in hot soup bowls and garnish each one with a little extra crème fraîche and some watercress leaves.
You will also need a saucepan with a capacity of about 6 pints (3.5 litres).