1. Cut the cabbage in half, remove and discard the core, and shred the cabbage finely.
2. Set a medium skillet over medium-high heat, add the oil, and heat to just below smoking.
3. Add the mustard seeds and cook until they begin to pop—approximately 15 to 20 seconds.
4. Lower the heat to medium and add the ginger. Cook for one minute.
5. Stir in the cabbage and mix well.
6. Add the turmeric and chili powder and mix well.
7. Pour in a tablespoon or two of water to prevent sticking.
8. Cook for 3 to 4 minutes or until the cabbage deepens in color, but retains its crunch. Do not overcook, or the vegetable will become mushy.
9. Remove from the heat and serve immediately.