In a bowl, mix cabbage with caraway seeds, sea salt and whey. Pound with a wooden pounder or a meat hammer for about 10 minutes to release juices. Place in a quart-sized, wide-mouth mason jar and press down firmly with a pounder or meat hammer until juices come to the top of the cabbage. The top of the cabbage should be at least 1 inch below the top of the jar. Cover tightly and keep at room temperature for about 3 days before transferring to cold storage. The sauerkraut may be eaten immediately, but it improves with age.