Heat half the oil in a deep frying pan. Add the pork, season to taste and cook for 5 minutes until browned all over. Remove from the pan and set aside. Add the remaining oil to the pan with the onion and cook for 5 minutes until softened.
Stir in the paprika, then add the tomatoes and potatoes. Season to taste, bring to the boil, then reduce the heat and simmer for 10 minutes.
Return the pork to the pan and cook for a further 5 minutes until the pork and potatoes are cooked through. Divide between serving bowls, top with the soured cream and serve sprinkled with parsley.