When the roast duck is done, start preparing the cabbage.
Cut off the leaves on the outside of the cabbage head and discard them. Shred the cabbage into strips (about 1 cm thick).
Place the cabbage in a pot along with the vinegar, the sugar and salt to taste and enough water to just about cover the cabbage. Bring to a boil and cover the pot with a lid and cook for 30 minutes. After this time, carefully drain away the water, then add the duck fat from the roast, and raisins to your liking.
Cook for another 5 minutes, until the remaining water has evaporated. Taste and adjust seasoning to your liking with more salt, sugar or vinegar.
Cover and cook for 30 minutes, then drain off the water, add 2 tbsp of duck fat and the raisins, and cook over low heat for a further five minutes, until the last drops of water have evaporated.
Season again, according to taste, with sugar, vinegar, and salt.