Peel the onions and cut into cubes. Wash the leek and cut into thin rings. Peel the carrots and cut into slices.
Heat the oil in a saucepan and sauté the onion, then the leek and the carrots. Pour in a good 1.2 liters of water, bring to the boil and stir in the broth. Simmer for about 10 minutes.
Cut the sausages into diamonds. Stir the puree powder into the soup, add the sausages. Heat for 1-2 minutes while stirring. Season the soup with salt, pepper and nutmeg.