Peel the carrots and cut into slices. Peel the apples and cut into wedges. Peel and dice the onions.
Heat the olive oil in a saucepan, sauté the onions, then add the carrots and apples and sauté briefly. Pour in the stock and milk and simmer over low heat for about 20 minutes until the vegetables are cooked through.
Peel the sausages and shape them into dumplings.
Finely puree the soup with a hand blender and bring to the boil briefly, insert the dumplings and let them steep in the soup for about 5 minutes.
Finally refine the soup with the sour cream, salt and pepper.