Peel and finely dice onions. Peel garlic and cut into thin slices. Rinse potatoes thoroughly, peel, rinse again and dice. Heat 3 tbsp. oil in a large saucepan, sauté onions, garlic and potatoes, turning, add clear soup, bring to a boil and simmer over medium heat for 20-25 minutes.
In the meantime, cut sausage into diagonal slices. Heat remaining oil in a frying pan, fry sausage slices in it, turning. Remove from frying pan and keep warm. Extinguish frying fat with whipping cream, briefly bring to the boil and cook a little.
Rinse chives, shake dry and cut into fine rolls. Remove a ladleful of potato cubes from the clear soup. Use a blender to mash remaining potatoes in the clear soup. Season soup with salt and freshly ground pepper to taste. Add sausage. Serve soup in dessert bowls, each with a dollop of whipped cream, a few potato cubes and sprinkled with chives.
Tip: As an alternative to fresh chives, you can also use the freeze-dried ones.