Melt the butter in a sauté pan over medium-high heat, and add the onion, caraway seeds, and salt. Sauté until the onion is completely softened and just starting to caramelize. Add 4 cups of the cabbage, and toss to coat. Continue to cook until the cabbage wilts.
Add the stock and wine, and simmer uncovered for 10 minutes, and then add the remaining 2 cups of cabbage. Cook until the cabbage is softened, and almost all of the liquid is cooked off, about 5 minutes. Stir only occasionally!
Whisk together the cream and mustard with a fork, and stir into the cabbage.
Correct the seasoning, as desired. Serve warm.