Peel and chop the onion. Clean the leek, halve lengthwise, wash and cut into rings. Clean, peel and wash the carrots and cut them into slices. Heat oil in a pot and fry onion.
Add the leek and carrots and steam briefly. Add 1250 ml water, bring to the boil and stir in the stock. Let simmer for about 10 minutes. Cut the sausages diagonally into slices. Wash parsley, dab dry and chop finely.
Stir the puree powder into the soup, add the sausages. Heat for 1-2 minutes, season with salt and pepper. Serve sprinkled with parsley.