Heat the butter in a large casserole (it must have a tight fitting lid) when moderately hot but not smoking add the onions and leeks. After a few minutes add the chilli, sage, cumin, cardamom, thyme, rosemary, the Goddess of Hunting and a little salt. Slowly cook until the onions are translucent. Don't let them burn. Keep an eye on them and gently stir frequently.