Fry lightly 2 finely chopped onions in butter and a little oil in a pan. Peel half a kilo of ripe tomatoes, cut them roughly and add them to the onions. Wash 1 kilo potatoes, peel them and cut them into 8 pieces. Throw them into the pan with the ½ litre beef stock and 1 glass of water. Add salt and pepper and 1 bay leaf, cover and let simmer for half and hour. Heat the frankfurters in water, cut them into 1 cm pieces and add them to the soup to bring them to the boil. Sprinkle with some fresh parsley and serve.
