Peel and dice the onion
Over medium heat, melt the goose fat in a large pot.
Add the onions and saute them until translucent.
In the meantime, remove the outer leaves of the cabbage and discard. Cut the cabbage into quarters and cut out the core at an angle. Cut the cabbage into fine strips.
Gradually add the cabbage to the onions.
Peel and cut the apple into small pieces.
Add the apple, bay leaf, cloves, vinegar, sugar, salt, and water to the cabbage.
Stir well. Cover the pot with a lid and turn the heat to low. Simmer the cabbage until soft, up to 2 hours. Check occasionally so that the bottom doesn't burn.
Season to taste with more salt, sugar, and/or vinegar.