Chop the onion and saute it in the oil in a saucepan for 2-3 minutes. Add the mustard seeds and cashews and cook for a further 2 minutes. Add the coriander, cumin, termeric and chili powder and cook for another minute. Chop the carrot and broccoli quite finely. Add to the saucepan along with the raisins and stir well. Pour in the water, bring to the boil, lower heat, cover pan and cook for 3-4 minutes. Season to taste. Pour in the farina very slowly, stirring all the time. As soon as it is all in the pan and well thickened, serve it, with the margarine spread over the top so that it melts into the mixture.