Soak green gram and rice together in water. After 2 hours, drain the soaked rice and gram, grind into a smooth paste, add salt to taste and if necessary adjust to a spreading consistency by diluting with water. Leave overnight to ferment. Chop the green chillies and onnions fine. Peel the ginger, chop fine. Mix green chillies, onions, ginger and coriander leaves together. HEat a griddle, smear it with ghee all over and spread the batter rather thick and round. Sprinkle the mixture of chopped ginger, onions, etc all over the batter, press lightly with the ladle so that the mixture slightly sinks into the batter. Pour tsp of ghee around the circumference of the batter and another tsp over the batter, where the mixture has sunk in. When the underside is cooked brown, cook the other side too similarly by pouring ghee around the circumference of the dosa. But then, the mixture need not be sprinkled over this side of the dosa, so pouring ghee over this side of the dosa does not arise. If you feel that the dosa could do with a hotter flavour, sprinkle more mixture over the batter. Serve hot.