Cabbage leaves have traditionally been used to treat engorgement by decreasing excess tissue swelling. When the swelling goes down the milk can flow more easily, relieving the engorgement. Reducing this inflammation makes mom much more comfortable.
If you're engorged, simply place the cabbage leaves (either chilled or at room temperature) on the skin of your breasts (stick them right in your bra). Leave them on until they wilt, and then apply new ones as often as needed for comfort. When engorgement is no longer a problem, you should discontinue use and throw out the rest of your cabbage.
(Or make a Reuben.)