Cut the cabbage into long thin shreds removing the tough stalks as you go.
Heat the oil in a large frying pan or wok. Add the onions and fry for 10-15 minutes , stirring from time to time, until soft and deep golden.
Add the cumin seeds and cook over a medium heat for a minute before adding the cabbage. Continue to fry on a moderate to high heat until the leaves are shiny and tender.
Add salt, pepper, chilli and garam masala then fry for 3-4 minutes, stirring constantly.