Place a small frying pan over low heat and dry-roast the cumin seeds until aromatic. Remove, then dry-roast the coriander seeds. Grind the roasted mixture to a fine powder using a spice grinder or pestle and mortar. In a food processor or with a knife, finely chop together the garlic, ginger and two-thirds of the onion.
Heat the oil in a karhai or casserole and fry the remaining onion u