Peel and finely chop the onions. Heat the fat. Fry the onions until translucent. Add peas. Deglaze with about 1/2 litre water, bring to the boil, cover and cook for about 15 minutes. Puree the peas in the cooking water. Season soup with salt and pepper
Stir the sour cream carefully into the soup. Wash and chop the parsley and sprinkle over the soup before serving