Heat 1 tablespoon of oil in a saucepan and add the diced potatoes and onions. As soon as the onions are translucent, add the 500 ml vegetable stock. Then cover and simmer everything over medium heat for about 10-12 minutes. Then puree with a hand blender and season with salt and pepper. Then cook for another 3 minutes. In the meantime, cut the two Vienna sausages into small pieces, add them to the soup and warm them up in the potato soup. Serve hot.