On the day before, finely chop the red cabbage (remove the stalk). Wash it, add the salt and knead with your hands until soft. Don't skip this step! Otherwise, i wont't come out as soft.
Add half of the goose fat to a large pot on medium heat and roast the onions until golden brown. Use the port to deglaze and cook for 1 minute.
Add vinegar, jam and honey. Add the cabbage and stir. Add a weight on top and let steep over night.
On the next day, add th remaining goose fat to a large pot on medium heat. Add the cabbage, orange zest, orange juice, and 1liter of water. Add salt and pepper to taste. Let simmer for 1 hour. Stir occssionally.
In the meantime, peel the potatoes and finely grate them.
After the 1 hour is over, add the grated potatoes, stir and bring to a boil. Reduce heat to medium and let simmer for another 30 minutes. Stir occssionally.
