Now add the tomatoes, garlic, cumin, salt and pepper. Leave to simmer for about 5 minutes and then add the potatoes. Next, fill the pot up to the 4 liter mark, if you are using a 3.5 liter pot, then up to the 3 liter mark and so on. Stir the whole thing again and bring to the boil. As soon as it bubbles, reduce the heat to medium and leave to boil for 20 minutes. Finally, add the smoked sausages, leave to reduce for 5 minutes, then season the potato soup with 1-2 tbsp Vegeta as required.