Melt the sugar in the saucepan and let it caramelize slightly. In the meantime, peel or clean the onions, potatoes and peppers. Then cut into cubes and sweat in the sugar. Deglaze with 1/4 l stock and reduce to a syrupy level. Add the sauerkraut, stir well and pour in the rest of the broth. Add the bay leaves, marjoram and peppercorns and let the soup steep for about 20 minutes more than boil. Sprinkle over frozen parsley before serving.