Sorrel soup recipe - Telegraph 500g/1lb floury potatoes, peeled and chopped into 2cm cubes 1 litre/35fl oz chicken stock 250g/8oz sorrel leaves, washed 2 egg yolks, beaten 200ml/7fl oz sour cream, plus extra to serve Chives and fennel tops, to garnish Melt the butter in a large, heavy-bottomed pan and add a splash of oil. Fry the onions and parsley with a pinch of salt until they are soft, about 3 minutes. Add the potatoes. Pour in the stock and bring to the boil. Cover with a lid and simmer for 15 minutes, or until the potatoes are completely tender. Roughly chop the sorrel leaves and add to the pan, then take off the heat. Transfer to a food processor (or use a hand blender) and blend until smooth. Beat the egg yolks and sour cream together in a bowl, then stir in two tablespoons of hot soup - you are doing this to prevent the eggs from scrambling. Very slowly whisk the egg and cream mix into the soup. Serve warm or chilled with a few snipped chives and fennel herbs.