First take away any stale or tough outer leaves from the cabbage; then, using a sharp knife, cut it into quarters and remove the tough stalky bits.
Now, leaving the quarters intact, wash them and dry them as thoroughly as possible. Pour the oil over the base of the casserole, add the crushed garlic and put it into the oven to heat through. Meanwhile crush the coriander seeds , preferably in a pestle and mortar but failing that you can use a small basin and the end of a rolling pin.
When the oil is hot and beginning to sizzle, add the crushed coriander seeds, then the pieces of cabbage. Baste each piece a little, season, put a lid on the casserole and put it back in the oven for about 40 minutes, or until the cabbage is tender when tested with a skewer.