Melt the fat in a deep pan and fry the sliced onion, carrot and parsnip until they begin to brown. Add the meat in ½ in. cubes, the paprika, the tomato roughly cut up, the bacon rinds and caraway seeds. Heat gently, stirring for a few minutes. Add the water and a pinch of salt and bring very slowly to simmering point. Simmer for 2 hr. Dice the potatoes and add them to the soup; continue simmering for another hour. Remove the bacon rinds. Season soup to taste and stir in the sour milk or yoghourt.